School Boy's research thread
01-21-2016, 01:48 PM
#1
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Join Date: May 2009
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School Boy's research thread
Since I'm always searching for new info and finding things not so easy to attain, I'm putting together a place to put all my info. THIS ALL WILL BE 96-04 RELATED! 
Mods, you might need to move this to the "(1996-2004 Modular) Mustang" I'm not sure but anyway.
My first contribute will be my "Recession Buster build" involving a budget 4.6 build.
https://mustangforums.com/forum/4-6l...ine-build.html
I will be adding several more articles/links throughout today as I dig them back up.
Mods, you might need to move this to the "(1996-2004 Modular) Mustang" I'm not sure but anyway.
My first contribute will be my "Recession Buster build" involving a budget 4.6 build.
https://mustangforums.com/forum/4-6l...ine-build.html
I will be adding several more articles/links throughout today as I dig them back up.
01-21-2016, 01:53 PM
#2
5th Gear Member
Thread Starter
Join Date: May 2009
Location: kentucky
Posts: 2,241
At Home Alignment
link to site
http://www.hotrod.com/how-to/chassis...ignment-guide/
Car Alignment Explained
Aligning a car may seem like one of those voodoo sciences that makes no sense if you've never actually seen it done, but as we learned by doing in preparing this article, the process is really quite straightforward if approached logically. The most difficult and time-consuming part of the process is setting up your equipment to get accurate, repeatable results. Most critical is having a flat, level spot to work from, and as you'll read, we've come up with a simple way to accomplish that so you can set alignment in your garage, shop, or even at the racetrack.
Although a bit more advanced and requiring more expensive tools than a basic alignment, we've also included information on measuring and adjusting bumpsteer and scaling and corner-weighting a car-techniques that are critical to properly setting up any race car or high-performance street machine for optimum handling.
Even if you're not racing, having all your car's wheels pointed in the right directions is a good idea, and you might be surprised at how much better your car drives after being aligned, not to mention the fact that your tires will probably last longer once you learn how to do your own alignments. Even if you just want to set it and forget it.
Step 1: Scaling and Cross-Weighting
Knowing your car's weight is handy, but knowing how that weight is balanced is critical for a race car and can be measured easily with the Longacre Accuset scale system, which costs about $1,100. If you don't need this advanced data, you can still use the information here about how to level the scales before moving on to the basic at-home alignment procedure in the following pages.
These diagrams show the before-and after results of corner-weighting our Mustang. Making a 1/2-inch ride height adjustment to the left rear resulted in a 1.1 percent increase in cross-weight to 49.2 percent, which represents 0.8 percent of reverse wedge. Notice that the left, rear, and total weights did not change. For more information on balancing the car's weight per wheel, see Marlan Davis' story "The Science of Scaling Your Car" in the Sept. '03 issue, or on the This Month page of HOTROD.com right now.
Scaling Tips
* Always measure cross-weights with the car in race-ready condition with all fluids full and driver weight accounted for.
* Develop a settling routine to use after each weight adjustment, either by rolling the car back and forth onto the scales or jouncing the suspension. Verify your procedure by weighing the car, jacking up one corner, and rechecking the corner-weights after settling. If the corner-weights vary, there is still some bind in the suspension. Refine your settling procedure until your results are repeatable before making any changes.
* Disconnect front and rear sway bars to eliminate the effect of sway-bar bind.
* Remember that weight jacking cannot shift weight from front-to-back or left-to-right. Only physically moving or adding weight can change the distribution within the car. (Small differences are the result of rounding.)
Your First Alignment
With some patience, it's actually very easy and cheap to set your wheel alignment at home. This page introduces you to the tools and basic terms you'll need to know. Refer to the previous section about scaling and cross-weighting to learn how to level all your wheel pads before you begin your alignment.
Alignment Terms
Ackerman Effect: Also called toe-out on turns, this occurs when the steering angle of the inside tire is greater than that of the outside tire when the wheels are turned. Ackerman is desirable because it helps the front end turn in to the corner.
Camber: The degree of deviation between the top edge of the tire and a true vertical line running through the center of the wheel. If the top of the tire tilts inward as seen from the front, camber is negative; if it tilts outward, camber is positive. A tire's traction is always greatest when the largest part of its contact patch is in contact with the road surface, and static camber can be dialed in to keep the tire perpendicular as the chassis rolls in a turn. Excessive camber results in accelerated wear on the inner or outer shoulders of the tires, but most street cars can benefit from up to 1-1.5 degrees of negative camber.
Caster: The deviation in degrees between an imaginary line running through the upper and lower ball joints and a vertical line running though the center of the wheel hub to the center of the tire's contact patch on the ground. If the imaginary line tilts to the back of the vehicle as viewed from the side, caster is positive; if it tilts forward, caster is negative. High amounts of positive caster cause the wheels to try to center themselves as the vehicle moves forward resulting in higher steering effort.
Cross-Camber: A side-to-side difference in camber settings. Many circle-track cars are set up to make lefthand turns with positive camber on the inside wheel and negative camber on the outside wheel.
Cross-Caster: A side-to-side difference in caster settings. Up to a half-degree more positive caster on the passenger side is often used on production vehicles to compensate for the effect of crowned pavement and keeps the vehicle from pulling to the outside edge of the road. Many oval-track racers run even higher amounts of cross-caster on the outside wheel to help the car turn down to a lefthand corner.
Toe Angle: Toe angle is the difference in track widths between the leading and trailing edges of the tires. If the track is wider at the front, the wheels are toed-out; if the track is narrower at the front, the wheels are toed in. Toe-in is used on most drag and production cars to compensate for slack in the steering components so the front wheels track straight ahead under forward thrust. Toe-out is often used on road-race cars to improve corner-entry turn-in, but excessive toe-out can cause dartiness on straightaways and tire wear.
Step 2: Measure Toe With the String Method
Very accurate toe measurements can be achieved by the string method, which involves stretching a perfectly squared rectangle of string around it to create a known point from which to measure. The simple-to-build rig consists of two lengths of 3/4-inch electrical conduit cut about 6 inches wider than the track width of the car, with holes drilled for the string to pass through on each end. The conduit is supported at each end of the car by a set of adjustable jackstands (we use screwdrivers to keep the conduit from rolling off, as seen in the photos) and a length of 60-pound-test fishing line is strung along each side of the car at the same height as the hubs. The string is squared by using a steel ruler to take measurements from fixed points on the chassis, such as the center of the wheel hubs or a machined flat on a wheel, and then sliding the conduit side-to-side until the string is an equal distance from the reference point on each side of the car. Note that the front and rear measurements may be different due to variations in track width, but the conduit ensures that the strings always remain parallel to each other. It will take several minutes of walking around the car making smaller and smaller adjustments until you get the string square. Record the measurements to speed up the process the next time. This will also help identify bent chassis parts in the future.
Tips on Setting Alignment
* The effects of the various alignment settings interact, so adjust caster and camber first. Toe must be set last.
* If you run out of adjustment range, you may have to make compromises on caster and camber to get the specs equal side-to-side.
* Always work from a level surface to avoid introducing error into your measurements. For example, tilting the front or rear of the car up or down can affect caster measurements. Tilting it side to side can affect the camber readings.
* Center the steering wheel before measuring and setting the toe, and make all adjustments without moving it.
Hrdp 0411 16 Z+DIY Wheel Alignment Guide+ 17/33
Step 3: Measure Camber
Camber measurements are easy with this inexpensive, yet highly accurate, caster/camber gauge from Maximum Motorsports, available for about $60. To use it, steer the wheels straight ahead (which is easy to get perfect if you have strung the car), then hold the gauge firmly against each wheel and turn the **** until the bubble level is centered. Each mark on the **** represents 1/8 degree of camber (clockwise for positive camber, counterclockwise for negative). That's it. Our road-race Mustang is set up with about 3 3/4 degrees of negative camber per side.
Step 4: Set Bumpsteer
Caused by the control arms and steering linkage traveling through arcs with unequal radiuses, bumpsteer results in the undesirable effect of the front wheels steering themselves without driver input as the suspension compresses and rebounds. The result forces the driver to make additional steering inputs to keep the car turning in the desired direction, especially in tight corners as the car's suspension rolls while cornering. The problem is noticeable on stock-suspended cars that have been lowered, but it's prevalent on street rods with fabricated front suspension.
Bumpsteer Tips
* Always set toe and caster prior to bumpsteering a car because caster affects the height of the steering arms, which in turn affects the bumpsteer measurements.
* Shoot for zero toe-in and no more than 0.015-0.020 inch of toe-out on bump, especially in the first inch of travel.
* Some toe-out on the inside tire in rebound can help corner entry by creating an Ackerman-like effect as the car turns in.
http://www.hotrod.com/how-to/chassis...ignment-guide/
Car Alignment Explained
Aligning a car may seem like one of those voodoo sciences that makes no sense if you've never actually seen it done, but as we learned by doing in preparing this article, the process is really quite straightforward if approached logically. The most difficult and time-consuming part of the process is setting up your equipment to get accurate, repeatable results. Most critical is having a flat, level spot to work from, and as you'll read, we've come up with a simple way to accomplish that so you can set alignment in your garage, shop, or even at the racetrack.
Although a bit more advanced and requiring more expensive tools than a basic alignment, we've also included information on measuring and adjusting bumpsteer and scaling and corner-weighting a car-techniques that are critical to properly setting up any race car or high-performance street machine for optimum handling.
Even if you're not racing, having all your car's wheels pointed in the right directions is a good idea, and you might be surprised at how much better your car drives after being aligned, not to mention the fact that your tires will probably last longer once you learn how to do your own alignments. Even if you just want to set it and forget it.
Step 1: Scaling and Cross-Weighting
Knowing your car's weight is handy, but knowing how that weight is balanced is critical for a race car and can be measured easily with the Longacre Accuset scale system, which costs about $1,100. If you don't need this advanced data, you can still use the information here about how to level the scales before moving on to the basic at-home alignment procedure in the following pages.
These diagrams show the before-and after results of corner-weighting our Mustang. Making a 1/2-inch ride height adjustment to the left rear resulted in a 1.1 percent increase in cross-weight to 49.2 percent, which represents 0.8 percent of reverse wedge. Notice that the left, rear, and total weights did not change. For more information on balancing the car's weight per wheel, see Marlan Davis' story "The Science of Scaling Your Car" in the Sept. '03 issue, or on the This Month page of HOTROD.com right now.
Scaling Tips
* Always measure cross-weights with the car in race-ready condition with all fluids full and driver weight accounted for.
* Develop a settling routine to use after each weight adjustment, either by rolling the car back and forth onto the scales or jouncing the suspension. Verify your procedure by weighing the car, jacking up one corner, and rechecking the corner-weights after settling. If the corner-weights vary, there is still some bind in the suspension. Refine your settling procedure until your results are repeatable before making any changes.
* Disconnect front and rear sway bars to eliminate the effect of sway-bar bind.
* Remember that weight jacking cannot shift weight from front-to-back or left-to-right. Only physically moving or adding weight can change the distribution within the car. (Small differences are the result of rounding.)
Your First Alignment
With some patience, it's actually very easy and cheap to set your wheel alignment at home. This page introduces you to the tools and basic terms you'll need to know. Refer to the previous section about scaling and cross-weighting to learn how to level all your wheel pads before you begin your alignment.
Alignment Terms
Ackerman Effect: Also called toe-out on turns, this occurs when the steering angle of the inside tire is greater than that of the outside tire when the wheels are turned. Ackerman is desirable because it helps the front end turn in to the corner.
Camber: The degree of deviation between the top edge of the tire and a true vertical line running through the center of the wheel. If the top of the tire tilts inward as seen from the front, camber is negative; if it tilts outward, camber is positive. A tire's traction is always greatest when the largest part of its contact patch is in contact with the road surface, and static camber can be dialed in to keep the tire perpendicular as the chassis rolls in a turn. Excessive camber results in accelerated wear on the inner or outer shoulders of the tires, but most street cars can benefit from up to 1-1.5 degrees of negative camber.
Caster: The deviation in degrees between an imaginary line running through the upper and lower ball joints and a vertical line running though the center of the wheel hub to the center of the tire's contact patch on the ground. If the imaginary line tilts to the back of the vehicle as viewed from the side, caster is positive; if it tilts forward, caster is negative. High amounts of positive caster cause the wheels to try to center themselves as the vehicle moves forward resulting in higher steering effort.
Cross-Camber: A side-to-side difference in camber settings. Many circle-track cars are set up to make lefthand turns with positive camber on the inside wheel and negative camber on the outside wheel.
Cross-Caster: A side-to-side difference in caster settings. Up to a half-degree more positive caster on the passenger side is often used on production vehicles to compensate for the effect of crowned pavement and keeps the vehicle from pulling to the outside edge of the road. Many oval-track racers run even higher amounts of cross-caster on the outside wheel to help the car turn down to a lefthand corner.
Toe Angle: Toe angle is the difference in track widths between the leading and trailing edges of the tires. If the track is wider at the front, the wheels are toed-out; if the track is narrower at the front, the wheels are toed in. Toe-in is used on most drag and production cars to compensate for slack in the steering components so the front wheels track straight ahead under forward thrust. Toe-out is often used on road-race cars to improve corner-entry turn-in, but excessive toe-out can cause dartiness on straightaways and tire wear.
Step 2: Measure Toe With the String Method
Very accurate toe measurements can be achieved by the string method, which involves stretching a perfectly squared rectangle of string around it to create a known point from which to measure. The simple-to-build rig consists of two lengths of 3/4-inch electrical conduit cut about 6 inches wider than the track width of the car, with holes drilled for the string to pass through on each end. The conduit is supported at each end of the car by a set of adjustable jackstands (we use screwdrivers to keep the conduit from rolling off, as seen in the photos) and a length of 60-pound-test fishing line is strung along each side of the car at the same height as the hubs. The string is squared by using a steel ruler to take measurements from fixed points on the chassis, such as the center of the wheel hubs or a machined flat on a wheel, and then sliding the conduit side-to-side until the string is an equal distance from the reference point on each side of the car. Note that the front and rear measurements may be different due to variations in track width, but the conduit ensures that the strings always remain parallel to each other. It will take several minutes of walking around the car making smaller and smaller adjustments until you get the string square. Record the measurements to speed up the process the next time. This will also help identify bent chassis parts in the future.
Tips on Setting Alignment
* The effects of the various alignment settings interact, so adjust caster and camber first. Toe must be set last.
* If you run out of adjustment range, you may have to make compromises on caster and camber to get the specs equal side-to-side.
* Always work from a level surface to avoid introducing error into your measurements. For example, tilting the front or rear of the car up or down can affect caster measurements. Tilting it side to side can affect the camber readings.
* Center the steering wheel before measuring and setting the toe, and make all adjustments without moving it.
Hrdp 0411 16 Z+DIY Wheel Alignment Guide+ 17/33
Step 3: Measure Camber
Camber measurements are easy with this inexpensive, yet highly accurate, caster/camber gauge from Maximum Motorsports, available for about $60. To use it, steer the wheels straight ahead (which is easy to get perfect if you have strung the car), then hold the gauge firmly against each wheel and turn the **** until the bubble level is centered. Each mark on the **** represents 1/8 degree of camber (clockwise for positive camber, counterclockwise for negative). That's it. Our road-race Mustang is set up with about 3 3/4 degrees of negative camber per side.
Step 4: Set Bumpsteer
Caused by the control arms and steering linkage traveling through arcs with unequal radiuses, bumpsteer results in the undesirable effect of the front wheels steering themselves without driver input as the suspension compresses and rebounds. The result forces the driver to make additional steering inputs to keep the car turning in the desired direction, especially in tight corners as the car's suspension rolls while cornering. The problem is noticeable on stock-suspended cars that have been lowered, but it's prevalent on street rods with fabricated front suspension.
Bumpsteer Tips
* Always set toe and caster prior to bumpsteering a car because caster affects the height of the steering arms, which in turn affects the bumpsteer measurements.
* Shoot for zero toe-in and no more than 0.015-0.020 inch of toe-out on bump, especially in the first inch of travel.
* Some toe-out on the inside tire in rebound can help corner entry by creating an Ackerman-like effect as the car turns in.
01-21-2016, 01:55 PM
#3
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Join Date: May 2009
Location: kentucky
Posts: 2,241
How to PROPERLY select and size TIRES for PERFORMANCE
How to PROPERLY select and size TIRES for PERFORMANCE
by Billy Johnson
The most important part of your car is not the engine, suspension, or brakes. It’s the TIRES!!! This is because your car can only perform as well as the capability of its tires. I’m often asked which tire is best and what size to buy. In this article I discuss my methods for choosing and properly sizing the right tires. I’m not into the “hella-flush” or “stance” scenes so this article is focused towards those who care about the PERFORMANCE of their car, whether on the street or on the track.
Pirelli had the best slogan for a tire company: “Power is nothing without control.” This is true for all forms of driving since it does not matter how much power you have if you can’t put it to the ground, it doesn’t matter how much you spend on a big brake kit if they easily lock up the tires, and your $7,000 coilovers can only deliver the performance that your tires are capable of. It really does not matter how great and expensive your car is or how much money you’ve put into modifying it if you cheap out on tires; which is the only component on your car that actually touches the road.
Tires are consumable and expensive, but this should not be a justification for crippling the handling of your sports car, sports sedan, or minivan. Whether you’re trying to break records and win races on the track or simply avoiding an accident on the street, choosing the right tire will often dictate the success of either.
There are 3 main steps that I follow when looking for tires: CHOOSE A TIRE CATEGORY, SIZE THE TIRE, and SELECT A TIRE. SIZE & SELECT A WHEEL is my fourth and last step when also looking for new wheels.
STEP 1: CHOOSE A TIRE CATEGORY
“What is the car being used for?”
Buying the right tires for your grocery-getting, baby-hauling daily driver in the northeast or Florida (where it rains most days of the week) is going to be a lot different than buying tires for your weekend toy in Southern California that never sees rain. Determining the importance of dry, wet, snow performance, tire longevity, ride quality, and comfort should be the first step when looking for a tire.
Just like everything in life, choosing the best tire is often a compromise since it’s rare to find a tire that is really good in the rain, quiet and lasts a long time that can perform well in the dry and hold up to extensive track use. Usually as you increase the dry capability of a tire, you start to suffer wet performance and comfort in terms of noise and ride quality. However, in recent years a few manufacturers are starting to make tires that are very good in all categories.
TireRack.com is a great source of information for everything tire related. They have numerous customer reviews, independent tests, and are a pleasure to do business with. They break down tires into 5 main categories, while I added a 6th. These 5 main categories are further broken down into sub-sections like “Ultra High Performance”, “High Performance”, “Performance”, “Touring”, etc… I won’t go into detail since I usually pick tires from the top sub-section of every category. I have arbitrarily listed some examples for each category below:
I often see really nice cars with a ton of money thrown at it in power upgrades and ‘blingy’ wheels wearing an improperly sized tire or something that is obviously not up to the capabilities of the car. Most people really do not understand the importance of their tires, not only from a performance standpoint but from a safety standpoint as well. This includes the age of the tire.
In order to have a better ‘show’, keep costs down, and regulate competition, most racing series use a “spec” tire. For those series that allow for more than one tire manufacturer, tire wars ensue and millions of dollars are spent in developing tires which often determine the success of a team or car.
1.Winter/Snow:
Bridgestone Blizzak, Michelin Alpin, Continental ContiWinterContact, Pirelli Winter Snowcontol
2.All-Season:
Michelin Pilot Sport A/S 3, Continental ExtremeContact DWS, P Zero All-Season
3.Summer:
Michelin Pilot Super Sport, Yokohama AD08R, Hankook R-S3, Dunlop ZII StarSpec, BFG Rival, Bridgestone RE-11, Pirelli P Zero Corsa System, Continental 5 & DW,
4.Streetable Track & Competition:
Michelin Pilot Sport Cup 2, Pirelli Trofeo R, Hankook Ventus TD, Continental ContiForceContact, Nitto NT01, Toyo R888, Yokohama A048
5. D.O.T. –Approved Slick:
Hoosier R7 & A7, BF Goodrich R1, Hankook Ventus Z214
6.Racing Slick:
Yokohama A005, Michelin, Hoosier, Pirelli
*Notice there is no “R-Compound” (“R” = Race Compound) tire definition in the above categories. “R-comp” is not really well defined other than the vague description of “race-derived rubber” and as a middle ground between street tires and racing slicks. This nomenclature is used for everything from the treaded NT01 and R888 to the slick A7, R7, and Ventus Z214. I prefer Tire Rack’s separation of the treaded “R-comps” into the Streetable Track & Competition category while placing tires with only circumferential grooves (like the Hoosier R7 & BFG R1) into the “D.O.T.-approved Slick” category.
Here’s a Top Tip:
“Tires are the most important. A narrower, but better (compound, construction, tread design, etc…) tire will, to a point, generally outperform a wider, inferior tire”.
STEP 2: SIZE THE TIRE
When sizing a tire, there are a few important things to know:
1. TIRE WIDTHS ARE USELESS.
I’m referring to the first number in the tire size code such as the “275” in a 275/35-18 tire. This may sound crazy because other than the diameter of the wheel, this is usually the most important aspect of the tire for many people. But hear me out: Have you ever tried a different brand of tire just to realize it does not fit the same as the ones you took off, or not even fit under your fenders at all? The reason for this is the tolerances tire manufactures have to follow when making a given tire size is substantial. Brand X’s 275 can be as wide as Brand Y’s 305! To make matters worse, there is no industry standard to establish how to measure tire tread widths.
Above is the "Specs" sheet for the Michelin Pilot Super Sport tire from TireRack.com. Here we see the 255/35-19 Michelin Pilot Super Sport above is produced in two different widths (one bespoke version for BMW), while the 275/35-18 is offered in three different widths (one bespoke for BMW) and the 315/35-20 is offered in two different bespoke Ferrari-specific widths. I added the ideal wheel width range on the far right for each tire's specific tread width (highlighted in yellow). The red arrow indicates the widest version of each tire size.
Often tire manufacturers will have multiple offerings or bespoke versions of the same size tire (as written on the sidewall). Due to the wide variance in tire construction, an auto manufacturer can specify not only the tread compound, design, and many aspects of the composition of the tire, but the width as well for the specific needs of a certain car. This further illustrates how the written number isn't all that usefull.
Most people are too focused on the number on their sidewall rather than the true width of the tire, or what will give them the best performance. I get it. Size matters for bragging rights just like the numbering on the side of a muscle car designating the car’s cubic displacement, or the chrome emblems on the side of a “hooptie” designating their wheel diameter. But this article is about optimizing performance; not a “whose is bigger” bragging rights. Instead we need to focus on the tire’s TREAD WIDTH.
2. TREAD WIDTH (THIS IS WHAT MATTERS):
TireRack.com has come to the rescue by establishing a common measurement method to address this issue!!! They literally measure every make, model and size of tire with the same test procedure using a 20” long tool with a 30-degree bend in it to measure the tread width of the tire to take account various tire shapes and radiuses. This number, measured in inches, is what I view as the true width of the tread, not what is written on the side wall, since Tire Rack uses the same measurement procedures for all of the different brand tires they sell.
3. SECTION WIDTH:
Is the measurement of the tire’s width from the inner sidewall to outer sidewall with the tire mounted on its industry assigned rim width at proper inflation pressures. This is not as important to me and is usually a bit wider than the tread width. A good rule of thumb to follow is that: for every 0.5” change in rim width, the tire’s section width will change by 0.2”.
4. MEASURING RIM WIDTH:
Is the industry standard rim width for which the tire must be mounted to meet its dimensional targets. AKA: the tire’s “Design rim width”. Without optimizing a tire’s performance, using this recommendation for rim width will be a quick and easy way to select your tire.
Here is a 285/35-20 Michelin Pilot Super Sport which has a 10.1" tread width (also available in a 10.5" tread width) mounted on a 20x10.5 wheel. This is a perfect tire-to-wheel sizing with a mild stretch, preloading the side wall just enough to improve steering response and performance.
*Billy’s rule of thumb:
“For ideal handling: when sizing a tire for a given wheel, I usually target a tire’s TREAD width to be as wide as the WHEEL width, or 0.5” narrower than the wheel width.”
From my personal experience working on and driving countless track days, time attacks, street cars and race cars, this typically optimizes the tire’s carcass for response and outright grip. It also gives the sidewall a very slight ‘stretch’ or preload, which will improve the tire’s response and break-away characteristics. OEM’s have to size tires to meet a ton of different targets like curb to wheel damage protection, cost, snow chain clearance (almost all cars have to take this into consideration) all which affects the decision on the size of the tire and is usually a compromise at the expense of peak performance.
Beauty is in the eye of the beholder and i'm not a huge fan of the 'hella-flush' trend; but this 225/40-14 Toyo T1R has a tread width more than 3 inches narrower than this 14x11 wheel. Not only is the tire at risk of coming off the bead when cornering, the ride quality and overall grip is negatively affected from this extreme stretch and would benefit from a much wider tire.
If a tire is too narrow for a given wheel width, the sidewall becomes overly preloaded and the carcass can distort to have uneven pressure across the surface of the tire. The preloaded sidewall also has greatly reduced flex and compliance, which would improve initial response, but it would ride poorly, be less forgiving over bumps, and the break-away characteristics would likely not be as predictable.
This 275/40-17 BFGoodrich g-Force KDW has a 10.8" tread width and is mounted on this relatively narrow 17x9 factory Firebird wheel. With a tread width nearly 2 inches wider then the rim width; this combination likely has a very vague and sloppy steering feel even if it increases peak grip over a properly sized 8.5" wide tire (245/40-17). A better option would be to source a 17x11 wheel for this tire.
On the other hand, if a tire is too wide for a given wheel width, the sidewall ‘bulges”. This usually results in sloppy handling characteristics, vague steering feel, excessive tread squirm, and the carcass of the tire can also distort and have uneven pressure across the surface of the tire.
….Okay, now with that education: “What are the constraints?”
Constraints could be as simple as the size of your current wheels and specific outer diameter needed to maintain the accuracy of the speedometer, odometer, traction control, and ABS functionality. Or it could be a little more in depth and limited by class specific rules (for competition) like maximum tire width, tread wear rating, or it can be very in depth with fitting the largest tire in the wheel well as possible.
1. Existing Wheels:
If you are not purchasing new wheels and are simply looking for new tires, look up the TREAD width of your current tires on TireRack.com –are they the same or 0.5” narrower than stock? If the tires are the OEM size, the tread width will probably be close to the rim width, and maybe even up to 0.5” wider.
For example: Let’s say your car has an 18x10” wheel and a Michelin Pilot Super Sport (PSS) tire on it from the factory. It’s likely the PSS would be a 285/35-18 for this wheel which has a 10.2” tread width. Now following my generic rule of thumb, the best size tire would be a 275/35-18 that has a 9.6” tread width which will improve the tire’s response and grip, but this is relative to the same 275 tire on a narrower wheel.
In our example, the factory 285 is pretty good but isn’t optimal for our 10” wheel, and it could make even more grip and have better response on a 10.5” wheel. If you were to downsize the tire on the factory 10” wheel, you are optimizing the grip and response of a smaller tire, but that may be a slight net loss of grip for a slight improvement of response. Depending on the situation, downsizing the tire could have slightly less, the same or slightly more grip. You can go either way here, but depending on your needs, I would probably keep the factory 285 width UNLESS a better performing tire can be had in the 275 width (and tread width) range, then that would be a win-win over an inferior 285. Remember the “Top Tip” earlier in the article?
2. Tire label width:
If you compete in time trials or wheel to wheel racing, but your class has a tire width limit of say, a 275. By now you should know at least two things: 1 - The sidewall tread width is useless and 2 - The tire model (compound/construction) is more important than width. Given a rule constraint like a 275, there is not much to do other than look at the true tread widths of the various tires and (more importantly) find out which compound is truly better.
3. Wheel well room:
This can get very complex when increasing the width and diameter of the tire beyond what the factory has intended; but there are 3 main things to consider: Width, Diameter, and Volume.
-WIDTH:
The width of a tire usually does not influence the ABS or Traction Control, and the constraints here tend to be limitations with steering lock and the tire rubbing the inner chassis at full lock. Optimizing the offsets and rim widths for the given amount of room is the goal here.
There are a few things to understand in regards to tire width. A WIDER TIRE:
Does NOT change the contact patch SIZE when the vehicle weight and tire pressure is the SAME.
DOES change the contact patch SHAPE when the vehicle weight and tire pressure is the SAME. The contact patch becomes wider and shorter (front to rear).
(Typically) ALLOWS for LOWER PRESSURE which will then INCREASE the contact patch size (good).
INCREASES the tires VOLUME, and makes it less prone to overheating and has a LONGER LIFE.
Takes LONGER to WARM UP to its ideal operating range. Usually not a problem on heavy cars.
by Billy Johnson
The most important part of your car is not the engine, suspension, or brakes. It’s the TIRES!!! This is because your car can only perform as well as the capability of its tires. I’m often asked which tire is best and what size to buy. In this article I discuss my methods for choosing and properly sizing the right tires. I’m not into the “hella-flush” or “stance” scenes so this article is focused towards those who care about the PERFORMANCE of their car, whether on the street or on the track.
Pirelli had the best slogan for a tire company: “Power is nothing without control.” This is true for all forms of driving since it does not matter how much power you have if you can’t put it to the ground, it doesn’t matter how much you spend on a big brake kit if they easily lock up the tires, and your $7,000 coilovers can only deliver the performance that your tires are capable of. It really does not matter how great and expensive your car is or how much money you’ve put into modifying it if you cheap out on tires; which is the only component on your car that actually touches the road.
Tires are consumable and expensive, but this should not be a justification for crippling the handling of your sports car, sports sedan, or minivan. Whether you’re trying to break records and win races on the track or simply avoiding an accident on the street, choosing the right tire will often dictate the success of either.
There are 3 main steps that I follow when looking for tires: CHOOSE A TIRE CATEGORY, SIZE THE TIRE, and SELECT A TIRE. SIZE & SELECT A WHEEL is my fourth and last step when also looking for new wheels.
STEP 1: CHOOSE A TIRE CATEGORY
“What is the car being used for?”
Buying the right tires for your grocery-getting, baby-hauling daily driver in the northeast or Florida (where it rains most days of the week) is going to be a lot different than buying tires for your weekend toy in Southern California that never sees rain. Determining the importance of dry, wet, snow performance, tire longevity, ride quality, and comfort should be the first step when looking for a tire.
Just like everything in life, choosing the best tire is often a compromise since it’s rare to find a tire that is really good in the rain, quiet and lasts a long time that can perform well in the dry and hold up to extensive track use. Usually as you increase the dry capability of a tire, you start to suffer wet performance and comfort in terms of noise and ride quality. However, in recent years a few manufacturers are starting to make tires that are very good in all categories.
TireRack.com is a great source of information for everything tire related. They have numerous customer reviews, independent tests, and are a pleasure to do business with. They break down tires into 5 main categories, while I added a 6th. These 5 main categories are further broken down into sub-sections like “Ultra High Performance”, “High Performance”, “Performance”, “Touring”, etc… I won’t go into detail since I usually pick tires from the top sub-section of every category. I have arbitrarily listed some examples for each category below:
I often see really nice cars with a ton of money thrown at it in power upgrades and ‘blingy’ wheels wearing an improperly sized tire or something that is obviously not up to the capabilities of the car. Most people really do not understand the importance of their tires, not only from a performance standpoint but from a safety standpoint as well. This includes the age of the tire.
In order to have a better ‘show’, keep costs down, and regulate competition, most racing series use a “spec” tire. For those series that allow for more than one tire manufacturer, tire wars ensue and millions of dollars are spent in developing tires which often determine the success of a team or car.
1.Winter/Snow:
Bridgestone Blizzak, Michelin Alpin, Continental ContiWinterContact, Pirelli Winter Snowcontol
2.All-Season:
Michelin Pilot Sport A/S 3, Continental ExtremeContact DWS, P Zero All-Season
3.Summer:
Michelin Pilot Super Sport, Yokohama AD08R, Hankook R-S3, Dunlop ZII StarSpec, BFG Rival, Bridgestone RE-11, Pirelli P Zero Corsa System, Continental 5 & DW,
4.Streetable Track & Competition:
Michelin Pilot Sport Cup 2, Pirelli Trofeo R, Hankook Ventus TD, Continental ContiForceContact, Nitto NT01, Toyo R888, Yokohama A048
5. D.O.T. –Approved Slick:
Hoosier R7 & A7, BF Goodrich R1, Hankook Ventus Z214
6.Racing Slick:
Yokohama A005, Michelin, Hoosier, Pirelli
*Notice there is no “R-Compound” (“R” = Race Compound) tire definition in the above categories. “R-comp” is not really well defined other than the vague description of “race-derived rubber” and as a middle ground between street tires and racing slicks. This nomenclature is used for everything from the treaded NT01 and R888 to the slick A7, R7, and Ventus Z214. I prefer Tire Rack’s separation of the treaded “R-comps” into the Streetable Track & Competition category while placing tires with only circumferential grooves (like the Hoosier R7 & BFG R1) into the “D.O.T.-approved Slick” category.
Here’s a Top Tip:
“Tires are the most important. A narrower, but better (compound, construction, tread design, etc…) tire will, to a point, generally outperform a wider, inferior tire”.
STEP 2: SIZE THE TIRE
When sizing a tire, there are a few important things to know:
1. TIRE WIDTHS ARE USELESS.
I’m referring to the first number in the tire size code such as the “275” in a 275/35-18 tire. This may sound crazy because other than the diameter of the wheel, this is usually the most important aspect of the tire for many people. But hear me out: Have you ever tried a different brand of tire just to realize it does not fit the same as the ones you took off, or not even fit under your fenders at all? The reason for this is the tolerances tire manufactures have to follow when making a given tire size is substantial. Brand X’s 275 can be as wide as Brand Y’s 305! To make matters worse, there is no industry standard to establish how to measure tire tread widths.
Above is the "Specs" sheet for the Michelin Pilot Super Sport tire from TireRack.com. Here we see the 255/35-19 Michelin Pilot Super Sport above is produced in two different widths (one bespoke version for BMW), while the 275/35-18 is offered in three different widths (one bespoke for BMW) and the 315/35-20 is offered in two different bespoke Ferrari-specific widths. I added the ideal wheel width range on the far right for each tire's specific tread width (highlighted in yellow). The red arrow indicates the widest version of each tire size.
Often tire manufacturers will have multiple offerings or bespoke versions of the same size tire (as written on the sidewall). Due to the wide variance in tire construction, an auto manufacturer can specify not only the tread compound, design, and many aspects of the composition of the tire, but the width as well for the specific needs of a certain car. This further illustrates how the written number isn't all that usefull.
Most people are too focused on the number on their sidewall rather than the true width of the tire, or what will give them the best performance. I get it. Size matters for bragging rights just like the numbering on the side of a muscle car designating the car’s cubic displacement, or the chrome emblems on the side of a “hooptie” designating their wheel diameter. But this article is about optimizing performance; not a “whose is bigger” bragging rights. Instead we need to focus on the tire’s TREAD WIDTH.
2. TREAD WIDTH (THIS IS WHAT MATTERS):
TireRack.com has come to the rescue by establishing a common measurement method to address this issue!!! They literally measure every make, model and size of tire with the same test procedure using a 20” long tool with a 30-degree bend in it to measure the tread width of the tire to take account various tire shapes and radiuses. This number, measured in inches, is what I view as the true width of the tread, not what is written on the side wall, since Tire Rack uses the same measurement procedures for all of the different brand tires they sell.
3. SECTION WIDTH:
Is the measurement of the tire’s width from the inner sidewall to outer sidewall with the tire mounted on its industry assigned rim width at proper inflation pressures. This is not as important to me and is usually a bit wider than the tread width. A good rule of thumb to follow is that: for every 0.5” change in rim width, the tire’s section width will change by 0.2”.
4. MEASURING RIM WIDTH:
Is the industry standard rim width for which the tire must be mounted to meet its dimensional targets. AKA: the tire’s “Design rim width”. Without optimizing a tire’s performance, using this recommendation for rim width will be a quick and easy way to select your tire.
Here is a 285/35-20 Michelin Pilot Super Sport which has a 10.1" tread width (also available in a 10.5" tread width) mounted on a 20x10.5 wheel. This is a perfect tire-to-wheel sizing with a mild stretch, preloading the side wall just enough to improve steering response and performance.
*Billy’s rule of thumb:
“For ideal handling: when sizing a tire for a given wheel, I usually target a tire’s TREAD width to be as wide as the WHEEL width, or 0.5” narrower than the wheel width.”
From my personal experience working on and driving countless track days, time attacks, street cars and race cars, this typically optimizes the tire’s carcass for response and outright grip. It also gives the sidewall a very slight ‘stretch’ or preload, which will improve the tire’s response and break-away characteristics. OEM’s have to size tires to meet a ton of different targets like curb to wheel damage protection, cost, snow chain clearance (almost all cars have to take this into consideration) all which affects the decision on the size of the tire and is usually a compromise at the expense of peak performance.
Beauty is in the eye of the beholder and i'm not a huge fan of the 'hella-flush' trend; but this 225/40-14 Toyo T1R has a tread width more than 3 inches narrower than this 14x11 wheel. Not only is the tire at risk of coming off the bead when cornering, the ride quality and overall grip is negatively affected from this extreme stretch and would benefit from a much wider tire.
If a tire is too narrow for a given wheel width, the sidewall becomes overly preloaded and the carcass can distort to have uneven pressure across the surface of the tire. The preloaded sidewall also has greatly reduced flex and compliance, which would improve initial response, but it would ride poorly, be less forgiving over bumps, and the break-away characteristics would likely not be as predictable.
This 275/40-17 BFGoodrich g-Force KDW has a 10.8" tread width and is mounted on this relatively narrow 17x9 factory Firebird wheel. With a tread width nearly 2 inches wider then the rim width; this combination likely has a very vague and sloppy steering feel even if it increases peak grip over a properly sized 8.5" wide tire (245/40-17). A better option would be to source a 17x11 wheel for this tire.
On the other hand, if a tire is too wide for a given wheel width, the sidewall ‘bulges”. This usually results in sloppy handling characteristics, vague steering feel, excessive tread squirm, and the carcass of the tire can also distort and have uneven pressure across the surface of the tire.
….Okay, now with that education: “What are the constraints?”
Constraints could be as simple as the size of your current wheels and specific outer diameter needed to maintain the accuracy of the speedometer, odometer, traction control, and ABS functionality. Or it could be a little more in depth and limited by class specific rules (for competition) like maximum tire width, tread wear rating, or it can be very in depth with fitting the largest tire in the wheel well as possible.
1. Existing Wheels:
If you are not purchasing new wheels and are simply looking for new tires, look up the TREAD width of your current tires on TireRack.com –are they the same or 0.5” narrower than stock? If the tires are the OEM size, the tread width will probably be close to the rim width, and maybe even up to 0.5” wider.
For example: Let’s say your car has an 18x10” wheel and a Michelin Pilot Super Sport (PSS) tire on it from the factory. It’s likely the PSS would be a 285/35-18 for this wheel which has a 10.2” tread width. Now following my generic rule of thumb, the best size tire would be a 275/35-18 that has a 9.6” tread width which will improve the tire’s response and grip, but this is relative to the same 275 tire on a narrower wheel.
In our example, the factory 285 is pretty good but isn’t optimal for our 10” wheel, and it could make even more grip and have better response on a 10.5” wheel. If you were to downsize the tire on the factory 10” wheel, you are optimizing the grip and response of a smaller tire, but that may be a slight net loss of grip for a slight improvement of response. Depending on the situation, downsizing the tire could have slightly less, the same or slightly more grip. You can go either way here, but depending on your needs, I would probably keep the factory 285 width UNLESS a better performing tire can be had in the 275 width (and tread width) range, then that would be a win-win over an inferior 285. Remember the “Top Tip” earlier in the article?
2. Tire label width:
If you compete in time trials or wheel to wheel racing, but your class has a tire width limit of say, a 275. By now you should know at least two things: 1 - The sidewall tread width is useless and 2 - The tire model (compound/construction) is more important than width. Given a rule constraint like a 275, there is not much to do other than look at the true tread widths of the various tires and (more importantly) find out which compound is truly better.
3. Wheel well room:
This can get very complex when increasing the width and diameter of the tire beyond what the factory has intended; but there are 3 main things to consider: Width, Diameter, and Volume.
-WIDTH:
The width of a tire usually does not influence the ABS or Traction Control, and the constraints here tend to be limitations with steering lock and the tire rubbing the inner chassis at full lock. Optimizing the offsets and rim widths for the given amount of room is the goal here.
There are a few things to understand in regards to tire width. A WIDER TIRE:
Does NOT change the contact patch SIZE when the vehicle weight and tire pressure is the SAME.
DOES change the contact patch SHAPE when the vehicle weight and tire pressure is the SAME. The contact patch becomes wider and shorter (front to rear).
(Typically) ALLOWS for LOWER PRESSURE which will then INCREASE the contact patch size (good).
INCREASES the tires VOLUME, and makes it less prone to overheating and has a LONGER LIFE.
Takes LONGER to WARM UP to its ideal operating range. Usually not a problem on heavy cars.
01-21-2016, 01:56 PM
#4
5th Gear Member
Thread Starter
Join Date: May 2009
Location: kentucky
Posts: 2,241
...Continued
-DIAMETER:
This has a huge influence on the ABS, Traction Control, speedometer, effective gear ratio, rotating mass, and much more. The easiest thing to do is to keep the diameter the same as the factory. I wouldn’t recommend going above or below this diameter until you know more about how it is going to affect the rest of the systems on your car.
Increasing the Diameter also changes the contact patch SIZE, making it longer (front to rear) and narrower (width) for a given vehicle weight and tire pressure. You can typically also lower tire pressures slightly to increase the contact patch due to a larger diameter tire. Larger diameter tires generally help for longitudinal grip (drag racing) more than a wider tire. There’s a reason drag racing tires have small diameter wheels, large sidewalls and very large outer diameter tires.
At one time, 18-inch wheels and anything smaller than a 40-series aspect ratio were considered 'blingy' and not for the performance-oriented; so everyone ran 17" wheels or smaller. You could say the same if you're older than I am for 15", 16" or 17" wheels. Now 18" wheels are the most popular size for performance tires on up to racing tires and manufacturers are increasing the overall wheel diameter of vehicles across the board to fit larger brakes for increasingly larger and heavier cars.
Keep in mind that larger diameters also increases the tire's VOLUME which can be advantageous. As far as sizing goes, this Ferrari 458 Speciale is arguably one of the best performance cars ever built and is equipped with massive 245/35-20 and 305/30-20 Michelin Pilot Sport Cup 2 tires that have 26.8" and 27.2" diameters respectively. Interestingly, the 300/650-18 and 320/710-18 racing slicks commonly used on GTE racecars have very similar outer diameters.
While slightly smaller brakes and either 18" or 19" wheels probably would have sufficed, Ferrari felt this direction of smaller sidewalls and larger diameter wheels were worth it and it's hard to argue against it especially when amazing supercars from the 918/P1/LaF trio to the Aventador SV, McLaren 675LT and Ford GT have all gone in this direction. Having driven the Speciale in bumpy pothole-riddled Toronto city streets, this package with its thin side wall heights isn't as bad as you might think in the worst conditions and is just brilliant on the racetrack.
-VOLUME:
Tire volume is an important and often overlooked aspect that directly affects a tire’s performance. Bigger isn’t always better and there’s a point of diminishing returns (which probably won’t be an issue for most readers) where a larger and wider tire will not be any faster. While a 245-width tire isn’t wide by today’s standards, Lotus Elise’s struggle to get heat into a 245 and tend to slip and slide on cold days due to their low weight and low center of gravity. On the other hand, a heavy 3,800lb car on 275s can lay down a fast lap or two but cannot last a 20 minute session without overheating the tires and being seconds off pace. All of this has to do with a tire’s VOLUME, which is dictated by the tire’s overall diameter and width.
emember that heavier cars need more volume from wider widths and increased diameters.
EXCEPTIONS:
There are always exceptions to every rule. A car’s setup is like an inter-connected spider web where changing anything influences everything else. Often one change will have a secondary effect that overshadows the primary change.
Because of this, it’s possible that running a tire a lot wider than the wheel width would improve the overall performance if it were on a heavy car, with a less than ideal alignment that is very heavy for the wheel width. In this case, the increased VOLUME of the tire, and tread width, would in fact improve the cornering ability of the car.
It’s important to understand the intended use of the car as well as the tire’s volume. You don’t want too much volume (like the Elise example) if you are autocrossing, because you will never heat the tire up to its ideal operating range in time to make grip. Likewise if you have a heavier car, increasing the volume is key to making tire last longer in a session.
Tire compound and tread design also plays a big role here and while swapping to a more aggressive tire is the easiest way to make a car faster and last longer before overheating the tires; increasing the volume will make the tires last even longer, and even allow for a tire choice that is less of a compromise for daily driving. Look at the following chart of various production cars and their weight-to-volume ratio:
Here we see various production cars and a few popular cars with commonly used track tire sizes sorted by Tire Loading (total tire volume/vehicle weight) from largest to smallest. Basically, how many square millimeters supports each pound of vehicle weight.
This figure is calculated by adding the total front and rear Tire Volumes (tire width x circumference) then dividing the total volume by the vehicle weight. The higher the mm per pound, the more the load is distributed across the tires and the more resilient the tire will be to overheating.
STEP 3: SELECT YOUR TIRE
“What tires fit your category and size?”
Now that you have determined what your tire is going to be used for and the respective tire category, and with the newfound knowledge of how to look at tires by their true size, it’s time to select a tire. But with all of the different stats and criteria out there, what factors make a tire good?
Feel free to read the definitions below but I’ll save you some time with this sentence:
Due to the subjective or interpretive nature of these tests; other than speed ratings (which may not apply to most people) all of the other tire performance criteria is for the most part USELESS.
Load Index
– You can read Tire Rack’s Load Index Definition if you want, but it’s basically the load carrying capacity of the tire, which usually isn’t important unless you’re making hundreds of pounds of downforce, have a heavy car, and are driving on an oval.
Speed Ratings
– Click the link above for more detail, but I mainly focus on tires with W (168mph), “99Y” (186mph), and “(99Y)” (Parentheses = 186mph+) based on the application. If you never go this fast (which you can’t do legally unless you’re on a racetrack, and even so, it’s rare to go this fast on track), then this probably does not matter.
Uniform Tire Quality Grade (UTQG)
– An arbitrary number originally developed to help consumers with a numerical value that represents the treadwear, traction, and temperature capabilities of the tire. Since the Department Of Transportation (DOT) does not test the tires and it’s up to the tire manufacturer to come up with the value, tire manufacturers set these numbers based on how they perceive the customer will understand how the tire will perform, or to meet a random number/standard that a racing series might restrict, to have a softer faster tire as an advantage. Because of all of this, UTQG is USELESS.
Treadwear Ratings:
A test based on a 7,200-mile test loop with routine tire pressure and rotation adjustments during it. A 100 rating should = the tread lasting the 7,200 miles, 200 rating = 2X that distance and so on. Since a lot is left open for interpretation and the only decently comparable data is from one tire to another within the same brand, this is also somewhat useless.
Traction Grade:
This is another useless test since it measures the deceleration g-forces of a locked tire across a WET road at 40mph. Other than seeing which tire will stop you the shortest distance with the tires locked; this is not relevant to cars with ABS or the braking ability of the tire under normal rack uses.
Temperature (Resistance) Grades:
Indicates the amount of heat generated by what appears to be an under-inflated tire at 85mph. Since this is also outside the scope of a properly maintained tire, I find it useless.
As tire technology gets better with each new design, often driven by what is learned in motorsports, tires are performing better in the dry and wet, are lasting longer, and are quieter than their predecessors. Keep in mind those manufacturers who are winning in multi-tire racing series tend to offer the best products to their customers as well.
These advancements make it difficult to properly classify a tire or draw conclusions that tire A lasts longer than Tire B because it’s Treadwear Rating is higher, or it will have more grip and wear out quicker because its UTQG is lower. Remember, these numbers are useless?
So back to the decision of selecting the best tire; when looking at TireRack’s subcategories
(“Ultra High Performance”, “High Performance”, “Performance”…) I usually look in the highest category. Price is usually a major factor in selecting a tire but since tires should be viewed as an INVESTMENT in terms of both performance and safety of your car, I rarely look below the second tier of subcategories.
When comparing tires within a category, the balancing of performance, comfort, and price begins.
TireRack’s rating table is going to be one of the best sources out there. Using a scale of 1-10, each tire is rated in terms of dry grip, steering response, wet grip, hydroplane resistance, road noise, longevity, etc… by consumer survey ratings which can be the average from hundreds of people. Having tracked many tires, I personally feel these figures are fairly accurate when comparing across brands and have the most credibility, especially compared to the useless UTQG or Treadwear ratings of a tire. The individual customer reviews of the tire can also be somewhat insightful, but I tend to take them with a grain of salt and use them as a secondary factor to TireRack’s rating system.
The tread design is something to consider when looking for tires. The design will usually reflect its performance in Tire Rack’s rating system, but in addition, looking at the outer shoulder, rain grooves and sipes will also give a vague idea of how they will perform. For track use, large continuous outer tread blocks will deliver more grip and stability than smaller tread blocks which tend to tear off and chunk. Larger tread blocks tend to be more prone to hydroplaning while tires with many, small tread blocks often perform better in rain and snow.
As you start comparing different tires, it’s important to verify the TREAD WIDTH of each model, and if they run too narrow or wide, shop to see if a slightly different size would be more applicable. If you are trying to break track records, further research would be beneficial but keep in mind that a review from a Lotus Elise owner on a set of tires probably won’t be as applicable on a heavy GTR or CTS-V, so try to find comments from someone with a car of similar weight and tire sizing.
I am not going to outright say buy this tire, or that tire sucks, but by now you have gained enough knowledge to make a more educated decision on your next set of tires with greater confidence that not only will the tires be more likely to fit, but will deliver the performance that you are looking for.
STEP 4: CHOOSING A WHEEL
Wheels are an expensive investment that will affect the handling, performance, and yes, looks of your car; so it’s important to do your homework before dropping a lot of cash down. This may sound backwards but since the tire is the most important part of your car, your wheel choice should be dictated by the tires you want to run.
When I look to increase the diameter and width of a set of wheels on a car, I define the goal of the increase, whether it’s to increase tire width for cornering, or volume (diameter and width) for prolonged track capability, or even simply for looks. Based on the available room in the wheel well, I then look at the availability of the group of tires in the general size that I want to go to, which narrows down the ideal wheel size that I should run.
If you are limited by room in the wheel well or rules for a particular class, the tires should be your limiting and deciding factor. Pick the best tire in the outer diameter and section width that will fit the room or rules, and then size the wheel accordingly.
This is the opposite from what almost everyone does. Most people buy bigger wheels based on looks and offsets and then the tire tends to be a compromised afterthought to fit those wheels in the remaining room that’s available. Since this article is about optimizing the performance of a car with tires, they should dictate what size wheel to run. In many cases, the ideal tire may not be available in the size that properly fits your wheels. If handling and performance is important to you, then your wheels will be sized accordingly. If you view form > function, then this article probably isn’t for you anyway.
For a daily driver where maximizing outright grip or tire volume may not be the top priority, choosing the widest tire possible may not be necessary at any expense of steering feel, fuel economy, and price. Remember the top tip?: "A narrower high quality tire will often outperform a cheap wider tire".
A proper amount of time should be spent on researching or measuring the wheel offsets and clearances of your current wheels to determine how much larger and wider of a tire can fit. Once the ideal tire is chosen, then you can select the diameter, width, and offset of your wheels. Staying the same or close to factory widths and offsets is a conservative way of making choosing a wheel much easier.
CONCLUSION
By now everyone should be an expert at sizing and selecting a tire, or at least possess a greater education on how tires are sized and what aspects are important when choosing a tire. By following the 3 main steps when looking for tires: CHOOSE A TIRE CATEGORY, SIZE THE TIRE, and SELECT A TIRE, it’s hard to go wrong.
Disclaimer: The information above is a recommendation for OFF ROAD USE only. Please consult and follow your owner’s manual when sizing tires for street use, otherwise follow the above advice at your own risk.
SOURCES:
BillyJohnsonRacing
link to article
http://www.corner-carvers.com/forums...ighlight=Tires
__________________
-DIAMETER:
This has a huge influence on the ABS, Traction Control, speedometer, effective gear ratio, rotating mass, and much more. The easiest thing to do is to keep the diameter the same as the factory. I wouldn’t recommend going above or below this diameter until you know more about how it is going to affect the rest of the systems on your car.
Increasing the Diameter also changes the contact patch SIZE, making it longer (front to rear) and narrower (width) for a given vehicle weight and tire pressure. You can typically also lower tire pressures slightly to increase the contact patch due to a larger diameter tire. Larger diameter tires generally help for longitudinal grip (drag racing) more than a wider tire. There’s a reason drag racing tires have small diameter wheels, large sidewalls and very large outer diameter tires.
At one time, 18-inch wheels and anything smaller than a 40-series aspect ratio were considered 'blingy' and not for the performance-oriented; so everyone ran 17" wheels or smaller. You could say the same if you're older than I am for 15", 16" or 17" wheels. Now 18" wheels are the most popular size for performance tires on up to racing tires and manufacturers are increasing the overall wheel diameter of vehicles across the board to fit larger brakes for increasingly larger and heavier cars.
Keep in mind that larger diameters also increases the tire's VOLUME which can be advantageous. As far as sizing goes, this Ferrari 458 Speciale is arguably one of the best performance cars ever built and is equipped with massive 245/35-20 and 305/30-20 Michelin Pilot Sport Cup 2 tires that have 26.8" and 27.2" diameters respectively. Interestingly, the 300/650-18 and 320/710-18 racing slicks commonly used on GTE racecars have very similar outer diameters.
While slightly smaller brakes and either 18" or 19" wheels probably would have sufficed, Ferrari felt this direction of smaller sidewalls and larger diameter wheels were worth it and it's hard to argue against it especially when amazing supercars from the 918/P1/LaF trio to the Aventador SV, McLaren 675LT and Ford GT have all gone in this direction. Having driven the Speciale in bumpy pothole-riddled Toronto city streets, this package with its thin side wall heights isn't as bad as you might think in the worst conditions and is just brilliant on the racetrack.
-VOLUME:
Tire volume is an important and often overlooked aspect that directly affects a tire’s performance. Bigger isn’t always better and there’s a point of diminishing returns (which probably won’t be an issue for most readers) where a larger and wider tire will not be any faster. While a 245-width tire isn’t wide by today’s standards, Lotus Elise’s struggle to get heat into a 245 and tend to slip and slide on cold days due to their low weight and low center of gravity. On the other hand, a heavy 3,800lb car on 275s can lay down a fast lap or two but cannot last a 20 minute session without overheating the tires and being seconds off pace. All of this has to do with a tire’s VOLUME, which is dictated by the tire’s overall diameter and width.
emember that heavier cars need more volume from wider widths and increased diameters.
EXCEPTIONS:
There are always exceptions to every rule. A car’s setup is like an inter-connected spider web where changing anything influences everything else. Often one change will have a secondary effect that overshadows the primary change.
Because of this, it’s possible that running a tire a lot wider than the wheel width would improve the overall performance if it were on a heavy car, with a less than ideal alignment that is very heavy for the wheel width. In this case, the increased VOLUME of the tire, and tread width, would in fact improve the cornering ability of the car.
It’s important to understand the intended use of the car as well as the tire’s volume. You don’t want too much volume (like the Elise example) if you are autocrossing, because you will never heat the tire up to its ideal operating range in time to make grip. Likewise if you have a heavier car, increasing the volume is key to making tire last longer in a session.
Tire compound and tread design also plays a big role here and while swapping to a more aggressive tire is the easiest way to make a car faster and last longer before overheating the tires; increasing the volume will make the tires last even longer, and even allow for a tire choice that is less of a compromise for daily driving. Look at the following chart of various production cars and their weight-to-volume ratio:
Here we see various production cars and a few popular cars with commonly used track tire sizes sorted by Tire Loading (total tire volume/vehicle weight) from largest to smallest. Basically, how many square millimeters supports each pound of vehicle weight.
This figure is calculated by adding the total front and rear Tire Volumes (tire width x circumference) then dividing the total volume by the vehicle weight. The higher the mm per pound, the more the load is distributed across the tires and the more resilient the tire will be to overheating.
STEP 3: SELECT YOUR TIRE
“What tires fit your category and size?”
Now that you have determined what your tire is going to be used for and the respective tire category, and with the newfound knowledge of how to look at tires by their true size, it’s time to select a tire. But with all of the different stats and criteria out there, what factors make a tire good?
Feel free to read the definitions below but I’ll save you some time with this sentence:
Due to the subjective or interpretive nature of these tests; other than speed ratings (which may not apply to most people) all of the other tire performance criteria is for the most part USELESS.
Load Index
– You can read Tire Rack’s Load Index Definition if you want, but it’s basically the load carrying capacity of the tire, which usually isn’t important unless you’re making hundreds of pounds of downforce, have a heavy car, and are driving on an oval.
Speed Ratings
– Click the link above for more detail, but I mainly focus on tires with W (168mph), “99Y” (186mph), and “(99Y)” (Parentheses = 186mph+) based on the application. If you never go this fast (which you can’t do legally unless you’re on a racetrack, and even so, it’s rare to go this fast on track), then this probably does not matter.
Uniform Tire Quality Grade (UTQG)
– An arbitrary number originally developed to help consumers with a numerical value that represents the treadwear, traction, and temperature capabilities of the tire. Since the Department Of Transportation (DOT) does not test the tires and it’s up to the tire manufacturer to come up with the value, tire manufacturers set these numbers based on how they perceive the customer will understand how the tire will perform, or to meet a random number/standard that a racing series might restrict, to have a softer faster tire as an advantage. Because of all of this, UTQG is USELESS.
Treadwear Ratings:
A test based on a 7,200-mile test loop with routine tire pressure and rotation adjustments during it. A 100 rating should = the tread lasting the 7,200 miles, 200 rating = 2X that distance and so on. Since a lot is left open for interpretation and the only decently comparable data is from one tire to another within the same brand, this is also somewhat useless.
Traction Grade:
This is another useless test since it measures the deceleration g-forces of a locked tire across a WET road at 40mph. Other than seeing which tire will stop you the shortest distance with the tires locked; this is not relevant to cars with ABS or the braking ability of the tire under normal rack uses.
Temperature (Resistance) Grades:
Indicates the amount of heat generated by what appears to be an under-inflated tire at 85mph. Since this is also outside the scope of a properly maintained tire, I find it useless.
As tire technology gets better with each new design, often driven by what is learned in motorsports, tires are performing better in the dry and wet, are lasting longer, and are quieter than their predecessors. Keep in mind those manufacturers who are winning in multi-tire racing series tend to offer the best products to their customers as well.
These advancements make it difficult to properly classify a tire or draw conclusions that tire A lasts longer than Tire B because it’s Treadwear Rating is higher, or it will have more grip and wear out quicker because its UTQG is lower. Remember, these numbers are useless?
So back to the decision of selecting the best tire; when looking at TireRack’s subcategories
(“Ultra High Performance”, “High Performance”, “Performance”…) I usually look in the highest category. Price is usually a major factor in selecting a tire but since tires should be viewed as an INVESTMENT in terms of both performance and safety of your car, I rarely look below the second tier of subcategories.
When comparing tires within a category, the balancing of performance, comfort, and price begins.
TireRack’s rating table is going to be one of the best sources out there. Using a scale of 1-10, each tire is rated in terms of dry grip, steering response, wet grip, hydroplane resistance, road noise, longevity, etc… by consumer survey ratings which can be the average from hundreds of people. Having tracked many tires, I personally feel these figures are fairly accurate when comparing across brands and have the most credibility, especially compared to the useless UTQG or Treadwear ratings of a tire. The individual customer reviews of the tire can also be somewhat insightful, but I tend to take them with a grain of salt and use them as a secondary factor to TireRack’s rating system.
The tread design is something to consider when looking for tires. The design will usually reflect its performance in Tire Rack’s rating system, but in addition, looking at the outer shoulder, rain grooves and sipes will also give a vague idea of how they will perform. For track use, large continuous outer tread blocks will deliver more grip and stability than smaller tread blocks which tend to tear off and chunk. Larger tread blocks tend to be more prone to hydroplaning while tires with many, small tread blocks often perform better in rain and snow.
As you start comparing different tires, it’s important to verify the TREAD WIDTH of each model, and if they run too narrow or wide, shop to see if a slightly different size would be more applicable. If you are trying to break track records, further research would be beneficial but keep in mind that a review from a Lotus Elise owner on a set of tires probably won’t be as applicable on a heavy GTR or CTS-V, so try to find comments from someone with a car of similar weight and tire sizing.
I am not going to outright say buy this tire, or that tire sucks, but by now you have gained enough knowledge to make a more educated decision on your next set of tires with greater confidence that not only will the tires be more likely to fit, but will deliver the performance that you are looking for.
STEP 4: CHOOSING A WHEEL
Wheels are an expensive investment that will affect the handling, performance, and yes, looks of your car; so it’s important to do your homework before dropping a lot of cash down. This may sound backwards but since the tire is the most important part of your car, your wheel choice should be dictated by the tires you want to run.
When I look to increase the diameter and width of a set of wheels on a car, I define the goal of the increase, whether it’s to increase tire width for cornering, or volume (diameter and width) for prolonged track capability, or even simply for looks. Based on the available room in the wheel well, I then look at the availability of the group of tires in the general size that I want to go to, which narrows down the ideal wheel size that I should run.
If you are limited by room in the wheel well or rules for a particular class, the tires should be your limiting and deciding factor. Pick the best tire in the outer diameter and section width that will fit the room or rules, and then size the wheel accordingly.
This is the opposite from what almost everyone does. Most people buy bigger wheels based on looks and offsets and then the tire tends to be a compromised afterthought to fit those wheels in the remaining room that’s available. Since this article is about optimizing the performance of a car with tires, they should dictate what size wheel to run. In many cases, the ideal tire may not be available in the size that properly fits your wheels. If handling and performance is important to you, then your wheels will be sized accordingly. If you view form > function, then this article probably isn’t for you anyway.
For a daily driver where maximizing outright grip or tire volume may not be the top priority, choosing the widest tire possible may not be necessary at any expense of steering feel, fuel economy, and price. Remember the top tip?: "A narrower high quality tire will often outperform a cheap wider tire".
A proper amount of time should be spent on researching or measuring the wheel offsets and clearances of your current wheels to determine how much larger and wider of a tire can fit. Once the ideal tire is chosen, then you can select the diameter, width, and offset of your wheels. Staying the same or close to factory widths and offsets is a conservative way of making choosing a wheel much easier.
CONCLUSION
By now everyone should be an expert at sizing and selecting a tire, or at least possess a greater education on how tires are sized and what aspects are important when choosing a tire. By following the 3 main steps when looking for tires: CHOOSE A TIRE CATEGORY, SIZE THE TIRE, and SELECT A TIRE, it’s hard to go wrong.
Disclaimer: The information above is a recommendation for OFF ROAD USE only. Please consult and follow your owner’s manual when sizing tires for street use, otherwise follow the above advice at your own risk.
SOURCES:
BillyJohnsonRacing
link to article
http://www.corner-carvers.com/forums...ighlight=Tires
__________________
01-21-2016, 02:00 PM
#5
5th Gear Member
Thread Starter
Join Date: May 2009
Location: kentucky
Posts: 2,241
IRS Tech
I found this info over on the svtp site and thought it was a good read. I personally have the irs in my GT and thought I would share the goods. Below is also a link to it. Also if a moderator can sticky, that would be awesome!
http://www.svtperformance.com/forums...S-Tech-Article
I. Preface
Here are my thoughts on the IRS. This is based on all information I have been able to collect on the 1999 - 2004 Mustang Cobra Independent Rear Suspension (or IRS for short). I know this is a lengthy read but it is well worth the time as it is intended to answer all technical questions about improving the 99-04 cobra IRS so please be patient and read carefully. I have taken great time to write this article to answer any questions you may have. If there is anything not covered or any changes, suggestions or questions feel free to contact me.
II. Introduction
The IRS must be looked at as a suspension system and addressed as such. There is no one part that will cure wheel hop. Let me say that again, there is no one part that will stop the hop. I get tons of questions about what part will fix their problem. Sorry but there is no magical part that will cure your wheel hop but I will attempt to tell you why it is happening and how to correct it permanently in all situations at any power level.
An origional sketch of the 99/01 Cobra IRS
A picture of the 99/01/03/04 Cobra IRS
III. Problem Description
A. Why the Cobra IRS hops
The problem with the IRS is Ford’s NVH (Noise Vibration and Harshness) engineers took the suspension as designed by SVT and determined that it was not luxurious enough for their special edition sports car and thusly recommended very soft bushings, springs and shocks to provide a more comfortable ride. What that left us with is an excellently designed performance suspension that was compromised for the sake of making the car ride smoother. What those engineers forgot is that this car was not designed to be a Rolls Royce. It is the last true muscle car and is driven by performance enthusiasts. And with access to aftermarket parts we can maintain that same ride quality but attain amazing performance as well with little to no trade off.
B. Hop and why it occurs
Suspension hop occurs when the rear tires are in a limited traction situation and the tires are allowed to move in unwanted directions. This means any time the car is trying to apply more power to the ground than tires, suspension and road conditions will allow. You can think of this just like when a drag racer smokes the tires, or a car spin the tires on the street. The IRS hops because when the tires begin grip the pavement and place load on the suspension the soft rubber bushings in the IRS allow the suspension components to move relative to each other in directions other than desired. This causes the tires gain and loose grip causing the suspension to oscillate between loaded and an unloaded state. This rapid uncontrolled movement is what you experience as wheel hop.
IV. Problem Solution
A. Overview
In order to gain and maintain traction you must keep the rear tires planted to the ground. Therefore good tires are a must. Obviously those tires must to be properly inflated to perform correctly. You also need to keep those tires on the ground so a good set of shocks and springs are very important. Coil-overs are best but stiff standard (non-coil over) springs will help but at the cost of ride harshness. Adjustable shocks are great for those who like to open track or drag, and they can be dialed in to combat wheel hop. Additionally in a coil-over arrangement they can be adjusted to match your spring rate. Needless to say subframe connectors are an absolute must. No suspension can be expected to perform properly if the chassis is not rigid and dependable. And possibly worst of all the IRS comes with soft rubber bushings in its attachment points, control arms and differential mounts. Even the 03/04s still use rubber though stiffer than 99/01s. Let’s look at this component by component.
B. Subframe Connectors
Subframe connectors should be the first modification done to a mustang. They improve every aspect of your cars performance. Griggs and Maximum Motorsports sell the best. MM's full length subframe connectors are the standard and most people will not need anything stronger. For those wanting the strongest frame possible go with Griggs Complete frame kit, also recommended for high horse power convertibles that don’t want to run a roll cage. Those wanting the ultimate look no further than Griggs World Challenge Frame Kit (note they are visible in the car but are the strongest mustang frame kit in the world).
Maximum Motorsports Full Length Subframe Connectors
Griggs Complete Frame Kit
Griggs World Challenge Frame Kit
C. Shocks
Shocks can be a matter of taste. Any of the top quality manufactures (Koni, Bilstein, Tokico, etc.) will offer quality shocks that will be better than the stock 99/01 offerings and a set of used 03/04 Bilsteins are an inexpensive but quality unit. You will want to choose your shock to match your struts in the front along with your springs and whether or not you plan to run them in a coil-over arraignment. I recommend going with a coil-over conversion for reasoning see the Q&A section. I have a Griggs coil-over kit with Koni adjustable shocks myself, and I recommend them over MMs IRS coil-over kits because Griggs installs spherical joints into the lower eyelets of their shocks where as MM uses polyurethane bushings which over time may fail. If you plan on using OE 03/04 cobra Bilsteins in a coil over application you will need MM's Upper Shock Mount Kit.
D. Springs
As stated before shocks and springs should be matched and you should determine if you wish to run coil-overs or stick to standard springs. If you choose to stick to standard springs you should make sure the spring you choose has a spring rate of 600lb/in or higher to avoid wheel hop. For the extreme budget minded a set of 03 coupe springs with one half coil cut will provide good results. If you are buying new consult with the shop you are buying from. Again I wouldn’t go anywhere but Griggs Racing or Maximum Motorsports.
E. Bushings
The rubber bushings in the IRS must be replaced. In my experience solid bushings are by far the best option. Polyurethane is a poor material for any moving part with a few notable exceptions. It is best to buy your bushings as a packaged kit as it is cheaper and you should replace all of them. The best kit to buy is AC427Cobra’s kit. It is complete, well engineered and performs exceptionally. Alternatively Maximum Motorsports offers a similar kit but at a higher cost and in my opinion with less refinement and engineering.
AC427Cobra’s Complete IRS Bushing Package
My Review of AC427Cobra’s Complete IRS Bushing Package
MM’s IRS Grip Box
1. Sway bar Bushings
While you are at it you should replace your rubber sway bar mount bushings with Maximum Motorsports urethane bushings. Note these are included in MM’s IRS Grip Box.
IRS Urethane Swabar Bushings
E. Braces and Other Fixes
1. Differential Ear Brace
1999 and 2001 cobras were not equipped with a brace that became standard on the 03/04 cobras. This brace adds two lower attachment points for the front of the differential pumpkin, making it more secure and lest prone to rotating under heavy acceleration. So all 99/01 owners will need to purchase an IRS heavy duty cross member (aka the differential ear brace or differential pinion support brace). I recommend the stock 03 brace as the aftermarket replicas are more expensive and offer no gain. The cheapest place I have found to purchase is Brown Brothers Performance Parts.
03 Cobra Cross Member
2. 12mm Bolt problem
Many 2003 and 2004 Cobras were erroneously fitted with 12mm bolts rather than 14mm bolts in the front mounting point of the IRS. This causes the IRS’s forward mount point to shift under load as the bolt is smaller than the sleeve in the bushing. There are several options to replace this bolt. First is to purchase the necessary hardware when buying your IRS bushing kit. AC427Cobra offers them as an add-on to the kit and Maximum Motorsports sells them separately (Bolt, Nut). The second option it to purchase them from your local Ford dealer. The part numbers you will need are W704939-S426 Bolt M14x109 H and W520215-S427 Nut M14 HEX FL.
3. Tire Clearance
Because of the Rear cantilever bracket clearance can be a problem when running wide rear tires. The rear subframe mounting bolts can be replaced with a button head design which allows bigger tires to be used without spacers or grinding on the OE bolt. Maximum Motorsports also offers such a bolt.
MM’s Low Profile IRS Subframe Bolts
For those who need additional wheel clearance with 10.5 inch wide replica style wheels (AFS, Replica Alloys, etc.) I recommend a set of billet wheel spacer from Lightning Force Performance. They will give you just enough clearance without pushing the wheel beyond the fender lip. I personally run 335/30/18 Viper spec Michelin Pilots on 18x10.5 AFS 03 cobra wheels with this spacer and a button head bolt with no clearance problems.
LFP’s 3/8” Hubcentric Wheel Spacer Kit
4. IRS Subframe Bracket Brace
The rear IRS subframe mounting point attaches to the car using a cantilevered bracket that is prone to flexing under load because the outer half of this bracket is completely unsupported. This flexing cause’s unwanted alignment changes and contributes to the IRS feeling like it is moving under the car. Billetflow's offers a subframe bracket brace that reinforces the rear mounts and eliminates flexing thus improving corning stability. Steeda offers a copy cat product for less money but Billetflow’s kit is stronger and better fitting.
Billetflow’s IRS Subframe Bracket Kit
Steeda’s IRS Subframe Bracket Kit
5. Pumpkin Cover Brace
To prevent the IRS differential cover from breaking when you launch you will want to pick up an IRS differential cover brace from Billetflow. This brace has held up for 800+ HP cars launching on slicks at the track and is cheap insurance against failure and damage.
Billetflow’s Differential Cover Brace
6. Shock Tower Brace
A shock tower brace improves rigidity and prevents chassis flex over the IRS (recommended if you run coil-overs). It is also advisable to weld the brace rather than bolt it in to add strength to the shock towers. If you are running coil overs with a stiff shock increased loads will cause additional stress on the mounts. A brace can be purchased from Hans RaceCraft. Kenny Brown used to make a brace that I liked more but they are now out of business but there are a few places you can still find one.
Hans Racecraft’s Rear Shock Tower Brace
Kenny Brown’s Rear Shock Tower Brace
F. Lowering and Associated Problems
1. Bumpsteer Issues
For cobras that have been lowered Maximum Motorsports makes adjustable IRS tie-rod ends that allow you to move the tie rod end back in to correct alignment. This is the equivalent of a bump steer kit for the IRS. Note there are 2 kits available in addition PHP’s toe link bars perform this function also see the section below for details. Also note that the Tie Rod Kit is included in MM’s IRS Grip box listed above.
MM’s Rear Tie Rod & Bumpsteer Kits
2. Toe-Link Bars
For high horsepower cars the rear toe link bars have been reported to flex. Paul’s High Performance and Maximum Motorsports offer a set of toe-link bars that replace the stock bars. The PHP bars are by far the beefiest of the bunch looking like a set of Honda half shafts. The Maximum Motorsports bars can be purchased separately or with the tie rod ends mentioned in the section above where as the PHP bars are only sold as a complete kit and eliminate the need for any of MM’s tie rod parts.
PHP’s IRS Toe Link Bars
MM’s Rear Tie Rod & Bumpsteer Kits
3. Sway bar Issues
Also when you lower the ride height of the IRS you change the position the sway bar rests at. Returning it to the original position will further improve the responsiveness and corning ability of the rear suspension at the lower ride height. Both AC427Cobra and Maximum Motorsports offer adjustable end links.
AC427Cobra’s Complete IRS Bushing Package
MM’s IRS Sway Bar End Link Set
4. Alignment Issues
Finally it is necessary to have your IRS aligned, see the alignment section below. If possible try to find a shop that can adjust your bump steer and corner weight your car if it is equipped with coil-overs.
G. Elevated Power Levels and Associated Problems
1. Half-Shafts
Now that you can plant your rear tires with confidence you may snap you half shafts though admittedly you were at greater risk when the rear end hopped. Regardless you may wish to purchase some stronger half shafts. Raxles makes half shafts for the 99/01 guys. A set of used 03 half shafts are a cheap upgrade for 01 owners who are near stock power levels. Remember they will not fit the 99s because 99s came with a 28 spline differential and half shafts where as 01s and 03s use 31 splines. Though you can upgrade your differential to a 31 spline unit and run those half shafts as well. If you want the strongest available the Driveshaft shop makes near indestructible half-shafts though they are not needed on the vast majority of cars.
Raxles
The Drive Shaft Shop’s Half Shaft Selection
2. Spindle Bearings
The stock spindle bearings have been known to wear prematurely under heavy track use and you may want to consider spherical spindle bearings. They are offered by Maximum Motorsports, Downunder Performance and Sean Hyland Motorsports. I do not run any of these products as of yet because my stock bearings are still in excelent condition so I can not offer a recomendation on over another.
MM IRS Cross-Axis Joint Replacement Kit
Downunder Performance
SHM’s Rear Upright Spherical Bearings
2. Differential Oil Cooler
A differential oil cooler may be advisable for those who frequently run open track events. I would make one yourself seeing as the kits I have found are overpriced. The parts list for the 2000 Cobra R diff cooler can be found here.
Parts List for 2000 Cobra R Differential Oil Cooler
V. Conclusion
If you follow this list of upgrades you will have an IRS that plants like a solid, handles like a Porsche, rides like a cloud (compared to a similar level 8.8) and is as close to bullet proof as possible.
http://www.svtperformance.com/forums...S-Tech-Article
I. Preface
Here are my thoughts on the IRS. This is based on all information I have been able to collect on the 1999 - 2004 Mustang Cobra Independent Rear Suspension (or IRS for short). I know this is a lengthy read but it is well worth the time as it is intended to answer all technical questions about improving the 99-04 cobra IRS so please be patient and read carefully. I have taken great time to write this article to answer any questions you may have. If there is anything not covered or any changes, suggestions or questions feel free to contact me.
II. Introduction
The IRS must be looked at as a suspension system and addressed as such. There is no one part that will cure wheel hop. Let me say that again, there is no one part that will stop the hop. I get tons of questions about what part will fix their problem. Sorry but there is no magical part that will cure your wheel hop but I will attempt to tell you why it is happening and how to correct it permanently in all situations at any power level.
An origional sketch of the 99/01 Cobra IRS
A picture of the 99/01/03/04 Cobra IRS
III. Problem Description
A. Why the Cobra IRS hops
The problem with the IRS is Ford’s NVH (Noise Vibration and Harshness) engineers took the suspension as designed by SVT and determined that it was not luxurious enough for their special edition sports car and thusly recommended very soft bushings, springs and shocks to provide a more comfortable ride. What that left us with is an excellently designed performance suspension that was compromised for the sake of making the car ride smoother. What those engineers forgot is that this car was not designed to be a Rolls Royce. It is the last true muscle car and is driven by performance enthusiasts. And with access to aftermarket parts we can maintain that same ride quality but attain amazing performance as well with little to no trade off.
B. Hop and why it occurs
Suspension hop occurs when the rear tires are in a limited traction situation and the tires are allowed to move in unwanted directions. This means any time the car is trying to apply more power to the ground than tires, suspension and road conditions will allow. You can think of this just like when a drag racer smokes the tires, or a car spin the tires on the street. The IRS hops because when the tires begin grip the pavement and place load on the suspension the soft rubber bushings in the IRS allow the suspension components to move relative to each other in directions other than desired. This causes the tires gain and loose grip causing the suspension to oscillate between loaded and an unloaded state. This rapid uncontrolled movement is what you experience as wheel hop.
IV. Problem Solution
A. Overview
In order to gain and maintain traction you must keep the rear tires planted to the ground. Therefore good tires are a must. Obviously those tires must to be properly inflated to perform correctly. You also need to keep those tires on the ground so a good set of shocks and springs are very important. Coil-overs are best but stiff standard (non-coil over) springs will help but at the cost of ride harshness. Adjustable shocks are great for those who like to open track or drag, and they can be dialed in to combat wheel hop. Additionally in a coil-over arrangement they can be adjusted to match your spring rate. Needless to say subframe connectors are an absolute must. No suspension can be expected to perform properly if the chassis is not rigid and dependable. And possibly worst of all the IRS comes with soft rubber bushings in its attachment points, control arms and differential mounts. Even the 03/04s still use rubber though stiffer than 99/01s. Let’s look at this component by component.
B. Subframe Connectors
Subframe connectors should be the first modification done to a mustang. They improve every aspect of your cars performance. Griggs and Maximum Motorsports sell the best. MM's full length subframe connectors are the standard and most people will not need anything stronger. For those wanting the strongest frame possible go with Griggs Complete frame kit, also recommended for high horse power convertibles that don’t want to run a roll cage. Those wanting the ultimate look no further than Griggs World Challenge Frame Kit (note they are visible in the car but are the strongest mustang frame kit in the world).
Maximum Motorsports Full Length Subframe Connectors
Griggs Complete Frame Kit
Griggs World Challenge Frame Kit
C. Shocks
Shocks can be a matter of taste. Any of the top quality manufactures (Koni, Bilstein, Tokico, etc.) will offer quality shocks that will be better than the stock 99/01 offerings and a set of used 03/04 Bilsteins are an inexpensive but quality unit. You will want to choose your shock to match your struts in the front along with your springs and whether or not you plan to run them in a coil-over arraignment. I recommend going with a coil-over conversion for reasoning see the Q&A section. I have a Griggs coil-over kit with Koni adjustable shocks myself, and I recommend them over MMs IRS coil-over kits because Griggs installs spherical joints into the lower eyelets of their shocks where as MM uses polyurethane bushings which over time may fail. If you plan on using OE 03/04 cobra Bilsteins in a coil over application you will need MM's Upper Shock Mount Kit.
D. Springs
As stated before shocks and springs should be matched and you should determine if you wish to run coil-overs or stick to standard springs. If you choose to stick to standard springs you should make sure the spring you choose has a spring rate of 600lb/in or higher to avoid wheel hop. For the extreme budget minded a set of 03 coupe springs with one half coil cut will provide good results. If you are buying new consult with the shop you are buying from. Again I wouldn’t go anywhere but Griggs Racing or Maximum Motorsports.
E. Bushings
The rubber bushings in the IRS must be replaced. In my experience solid bushings are by far the best option. Polyurethane is a poor material for any moving part with a few notable exceptions. It is best to buy your bushings as a packaged kit as it is cheaper and you should replace all of them. The best kit to buy is AC427Cobra’s kit. It is complete, well engineered and performs exceptionally. Alternatively Maximum Motorsports offers a similar kit but at a higher cost and in my opinion with less refinement and engineering.
AC427Cobra’s Complete IRS Bushing Package
My Review of AC427Cobra’s Complete IRS Bushing Package
MM’s IRS Grip Box
1. Sway bar Bushings
While you are at it you should replace your rubber sway bar mount bushings with Maximum Motorsports urethane bushings. Note these are included in MM’s IRS Grip Box.
IRS Urethane Swabar Bushings
E. Braces and Other Fixes
1. Differential Ear Brace
1999 and 2001 cobras were not equipped with a brace that became standard on the 03/04 cobras. This brace adds two lower attachment points for the front of the differential pumpkin, making it more secure and lest prone to rotating under heavy acceleration. So all 99/01 owners will need to purchase an IRS heavy duty cross member (aka the differential ear brace or differential pinion support brace). I recommend the stock 03 brace as the aftermarket replicas are more expensive and offer no gain. The cheapest place I have found to purchase is Brown Brothers Performance Parts.
03 Cobra Cross Member
2. 12mm Bolt problem
Many 2003 and 2004 Cobras were erroneously fitted with 12mm bolts rather than 14mm bolts in the front mounting point of the IRS. This causes the IRS’s forward mount point to shift under load as the bolt is smaller than the sleeve in the bushing. There are several options to replace this bolt. First is to purchase the necessary hardware when buying your IRS bushing kit. AC427Cobra offers them as an add-on to the kit and Maximum Motorsports sells them separately (Bolt, Nut). The second option it to purchase them from your local Ford dealer. The part numbers you will need are W704939-S426 Bolt M14x109 H and W520215-S427 Nut M14 HEX FL.
3. Tire Clearance
Because of the Rear cantilever bracket clearance can be a problem when running wide rear tires. The rear subframe mounting bolts can be replaced with a button head design which allows bigger tires to be used without spacers or grinding on the OE bolt. Maximum Motorsports also offers such a bolt.
MM’s Low Profile IRS Subframe Bolts
For those who need additional wheel clearance with 10.5 inch wide replica style wheels (AFS, Replica Alloys, etc.) I recommend a set of billet wheel spacer from Lightning Force Performance. They will give you just enough clearance without pushing the wheel beyond the fender lip. I personally run 335/30/18 Viper spec Michelin Pilots on 18x10.5 AFS 03 cobra wheels with this spacer and a button head bolt with no clearance problems.
LFP’s 3/8” Hubcentric Wheel Spacer Kit
4. IRS Subframe Bracket Brace
The rear IRS subframe mounting point attaches to the car using a cantilevered bracket that is prone to flexing under load because the outer half of this bracket is completely unsupported. This flexing cause’s unwanted alignment changes and contributes to the IRS feeling like it is moving under the car. Billetflow's offers a subframe bracket brace that reinforces the rear mounts and eliminates flexing thus improving corning stability. Steeda offers a copy cat product for less money but Billetflow’s kit is stronger and better fitting.
Billetflow’s IRS Subframe Bracket Kit
Steeda’s IRS Subframe Bracket Kit
5. Pumpkin Cover Brace
To prevent the IRS differential cover from breaking when you launch you will want to pick up an IRS differential cover brace from Billetflow. This brace has held up for 800+ HP cars launching on slicks at the track and is cheap insurance against failure and damage.
Billetflow’s Differential Cover Brace
6. Shock Tower Brace
A shock tower brace improves rigidity and prevents chassis flex over the IRS (recommended if you run coil-overs). It is also advisable to weld the brace rather than bolt it in to add strength to the shock towers. If you are running coil overs with a stiff shock increased loads will cause additional stress on the mounts. A brace can be purchased from Hans RaceCraft. Kenny Brown used to make a brace that I liked more but they are now out of business but there are a few places you can still find one.
Hans Racecraft’s Rear Shock Tower Brace
Kenny Brown’s Rear Shock Tower Brace
F. Lowering and Associated Problems
1. Bumpsteer Issues
For cobras that have been lowered Maximum Motorsports makes adjustable IRS tie-rod ends that allow you to move the tie rod end back in to correct alignment. This is the equivalent of a bump steer kit for the IRS. Note there are 2 kits available in addition PHP’s toe link bars perform this function also see the section below for details. Also note that the Tie Rod Kit is included in MM’s IRS Grip box listed above.
MM’s Rear Tie Rod & Bumpsteer Kits
2. Toe-Link Bars
For high horsepower cars the rear toe link bars have been reported to flex. Paul’s High Performance and Maximum Motorsports offer a set of toe-link bars that replace the stock bars. The PHP bars are by far the beefiest of the bunch looking like a set of Honda half shafts. The Maximum Motorsports bars can be purchased separately or with the tie rod ends mentioned in the section above where as the PHP bars are only sold as a complete kit and eliminate the need for any of MM’s tie rod parts.
PHP’s IRS Toe Link Bars
MM’s Rear Tie Rod & Bumpsteer Kits
3. Sway bar Issues
Also when you lower the ride height of the IRS you change the position the sway bar rests at. Returning it to the original position will further improve the responsiveness and corning ability of the rear suspension at the lower ride height. Both AC427Cobra and Maximum Motorsports offer adjustable end links.
AC427Cobra’s Complete IRS Bushing Package
MM’s IRS Sway Bar End Link Set
4. Alignment Issues
Finally it is necessary to have your IRS aligned, see the alignment section below. If possible try to find a shop that can adjust your bump steer and corner weight your car if it is equipped with coil-overs.
G. Elevated Power Levels and Associated Problems
1. Half-Shafts
Now that you can plant your rear tires with confidence you may snap you half shafts though admittedly you were at greater risk when the rear end hopped. Regardless you may wish to purchase some stronger half shafts. Raxles makes half shafts for the 99/01 guys. A set of used 03 half shafts are a cheap upgrade for 01 owners who are near stock power levels. Remember they will not fit the 99s because 99s came with a 28 spline differential and half shafts where as 01s and 03s use 31 splines. Though you can upgrade your differential to a 31 spline unit and run those half shafts as well. If you want the strongest available the Driveshaft shop makes near indestructible half-shafts though they are not needed on the vast majority of cars.
Raxles
The Drive Shaft Shop’s Half Shaft Selection
2. Spindle Bearings
The stock spindle bearings have been known to wear prematurely under heavy track use and you may want to consider spherical spindle bearings. They are offered by Maximum Motorsports, Downunder Performance and Sean Hyland Motorsports. I do not run any of these products as of yet because my stock bearings are still in excelent condition so I can not offer a recomendation on over another.
MM IRS Cross-Axis Joint Replacement Kit
Downunder Performance
SHM’s Rear Upright Spherical Bearings
2. Differential Oil Cooler
A differential oil cooler may be advisable for those who frequently run open track events. I would make one yourself seeing as the kits I have found are overpriced. The parts list for the 2000 Cobra R diff cooler can be found here.
Parts List for 2000 Cobra R Differential Oil Cooler
V. Conclusion
If you follow this list of upgrades you will have an IRS that plants like a solid, handles like a Porsche, rides like a cloud (compared to a similar level 8.8) and is as close to bullet proof as possible.
01-21-2016, 02:01 PM
#6
5th Gear Member
Thread Starter
Join Date: May 2009
Location: kentucky
Posts: 2,241
IRS Tech
VI. Q & A
Q. Why shouldn’t I just swap in a solid axle rather than build my IRS?
If you choose to swap your IRS for a solid rear axel that is your decision but I believe you are making the wrong decision and Chuck Schwynoch of Maximum Motorsports agrees with me.
NASA Pro Racing – Interview with Chuck Schwynoch, CEO
Maximum Motorsports, Inc.
June 28, 2006
By Andy Bowman
Q. The #91 MM Mustang is using an IRS rear suspension, what drove you to this decision, how has the effort been going so far?
A. We had a growing number of customers who called us and said that they were not happy with their IRS, and asked us if they should swap in the proven MM Torque-arm/Panhard Bar rear suspension. We couldn't give them a truthful answer until we had done our own testing to directly compare the Ford IRS to a well-sorted Torque-arm/Panhard bar system. Our AI race car had won races, and set track records, so it was the perfect candidate for comparison. We swapped the rear end over to the IRS, with all of the parts we had developed over the previous year on a street-driven 2003 Cobra. We left the front of the car exactly as it was with the Torque arm suspension. We maintained the exact same rear track width, and even swapped over the same brakes, rotors, calipers, and pads, from the solid axle. We then hit the track for testing. By the end of the first day of testing we were 3 seconds under the AI track record at Buttonwillow. With the IRS we had to learn what alignment and bumpsteer settings worked best. That's what testing told us. Without track testing, we really could not have given our customers an honest answer to their questions about the IRS. Even if our testing had shown the IRS to be grossly inferior to a solid axle, we at least would then be able to help our customers make an informed decision about modifying their car. As it turned out, the IRS is superior to a solid axle fitted with a Torque-arm and Panhard bar, in most aspects. And he is speaking of a Torque-arm/Panhard bar built solid rear vs. a built IRS. A stock four link solid rear is a joke by comparison. If they race it competitively in a very demanding series and they are a suspension/race shop and they say it is faster and better in most ways I'd tend to believe them. Add that to the fact that every world class sports car has an independent suspension. I don't think SVT was trying to install an inferior suspension in the top line car.
Q. Isn’t building the IRS more expensive than a built solid axel?
No. For instance the Maximum Grip Box from Maximum Motorsports for the SRA costs MORE than the Maximum Grip Box for the IRS. So there goes that argument (as seen here). Not to mention that ac427cobra's bushing kit costs a fraction of what MM's do...
Q. Are the Install costs for a built IRS more than a torque arm/panhard rod SRA?
I can tell you that it costs more to weld parts on to a car and setup a new suspension than to replace bushings and bolt on a few parts for the IRS.
Q. Even with a built IRS as described above wont the IRS still break?
The only parts that can fail in the IRS once properly built as described above are the Diff (same as in a SRA) and the half shfts instead of the axles in a SRA. If you have a properly articulating suspension you will not break 03 half shafts unless you are running extreme power at the strip (and most aren't). If you are then yes you may want to look in to DSS shafts but 03 shafts are just as strong as stock SRA axles. Just because some uninformed people when out to the strip and broke some shafts before knowing that modifications were needed to prevent part breakage doesn't mean it is an inferior suspension. That is like saying the SRA is crap because some people ripped their torque boxes up. They didn't know that they needed to weld some bracing not the suspensions fault.
Q. The solid rear axel seems to be fine right out of the box why shouldn’t I just run that?
The SRA is a poorly designed suspension and that is well documented...
Taken from the Griggs Racing website
An even larger concern is found in the rear suspension. Ford uses a 4-link design, but with the upper two control arms angled heavily outward. This means the lower and upper rear control arms are not parallel, so as the suspension moves the upper arms are twisted in their bushings. During performance driving this quickly leads to a near total binding of the rear suspension, called roll bind. With the axle bound, it acts like a giant anti-sway bar, causing the rear roll stiffness to skyrocket and the overloaded rear tires to loose traction and spin. This is why the rear end snaps into uncontrollable fishtailing when cornering, and it is also why the rear tires break loose at the drag strip once the body starts rising from the initial power hit. And Griggs is a strong propionate of the Torque Arm, Panhard Bar SRA. I know Bruce Griggs personally and he and I have had discussions about the topic a few different times. He doesn't like the built IRS in comparison to a built SRA but one thing we completely agree on is that the Fox and SN95 SRAs are totally unacceptable as delivered from the factory. I run his front suspension and it is amazing, I also run a few of his rear parts but for the most part the rear of my car is a mix of parts all working together to create super car like handling and performance. Based on what can be saved on parts and labor costs, a built IRS is a cheaper, less labor intensive, and superior suspension in all cases to a built SRA (except dedicated drag race cars).
Q. Won’t the delrin bushing squeak eventually?
With grease fittings installed you should never have squeaking. All you have to is have a technician shoot some grease in to the joints every few oil changes and your done. I have had delrin bushings in my Griggs front control arms for years now and all I have to do is add some grease about every 2 years or so you can probably expect similar results in the IRS but your mileage may vary.
Q. Do I need level 5 half shafts?"
Most likely not, but it depends. The 1999 half shafts are really not sufficient for mildly to highly modded cars drag racing with slicks or DR's even after you remove all of the rubber preventing wheel hop. I say run them till you break them but you most likely will. Your best bet at that point would be to purchase better shafts from Raxles or upgrade to a 31 spline differential and install '03 half shafts. 01 owners face the same situation but would not need to upgrade the differential to run 03 half shafts. If you then break one of the '03 Ford half shafts, and you have already removed all of the rubber from your IRS assembly, you need to look at DSS shafts.
Q. What if I already broke a 03 half shaft?
If you have then it may be time to upgrade, but only if you've removed all of the rubber in your IRS assembly and still broke a half shaft. More half shafts have been broken due to wheel hop directly caused by the components mounted in rubber, than broken because of sheer power. Once all rubber is removed from the IRS assembly and you break a half shaft, then by all means you're a candidate for DSS shafts.
Q. What is bump steer?
Bumpsteer is the term for the situation when the toe angle of a wheel changes as the suspension moves up and down, such as when driving over bumps, or with body roll during cornering. This happens when the arc that the spindle travels during bump and droop is not the same as the arc of the outer tie-rod end. If the toe changes more than a very small amount, the rear wheels begin steering the car.
Q: "How important is bump steering the IRS?"
Bump steering the IRS is not required but highly recommended and you will notice a difference.
Q: "Why do I hear a clunk in my drivetrain?"
There are a few likely reasons for the clunk. Your transmission and gears can combine for quite a bit of play, but that usually is not the main source of the "clunk". A few different things can contribute to the Cobra "clunk". The most likely are the bushings the differential is mounted with. The rubber OEM differential bushings are soft and spongy. Defiantly not the kind of material I would select to mount a component that is expected to translate all the driveshaft’s rotational force to the half shafts. These soft bushings allow the differential to move and that clunk you hear is most likely that movement. The situation is even worse for 99/01 owners because the bushings for those years were even softer and Ford had not yet developed the differential support brace. See section E1 for further details.
An alternative reason could be the front subframe mounting bolts. On some 2003 and 2004 cobras Ford accidently installed 12mm bolts rather than 14mm bolts that allow the subframe to shift during acceleration and breaking and cornering. Larger bolts will remedy this situation see section E12.
Q. Wont the suspension be more noisy with all those solid bushings?
Yes and No. I didn't notice any additional vibration or harshness because any bumps or road irregularities are transmitted to the suspension rather than the car. The solid bushings in most locations should not add any NVH to your car but the solid bushings used to mount the differential will increase your cabin noise but nothing terrible and certainly not a deal breaker IMO. But as I said in my review the noise increase is equivalent to installing an aftermarket shifter without installing a shifter gasket or any noise canceling material. You just hear a little more gear whine from the differential after it is solidly mounted. If you are worried about it buy some Dynamat and you will be fine.
Q. I’ve heard that drag radials will cure my wheel hop, is that true?
They will help but that is far from a solution those that say buy some drag radials and you will be fine are wrong. Maybe if you drive like a grandmother then yes you don’t have wheel hop anymore but your recipe won’t work for the rest of us.
Q. Why does my IRS hop more now than it used to?
The suspension performs better when it is new because the rubber has yet to soften up and begin to deteriorate. This means they allow even more undesirable suspension movement.
Q. What is the difference between the 03/04 IRS and the 99/01 IRS?
From 99 the 01's had 31 spline diff and half shafts which was no real improvement as the spline count was not the problem. The 99 & 01 shafts taper down at the CV boot and create a weak point. The 03 Shafts are a constant diameter and are by comparison much stronger. The 03's also had stiffer bushings along with better shocks, stiffer springs, the addition of a forward differential pinion brace, and lower inner toe control mounting points. These improvements made it handle a little better, improved durability and reduced bump steer. Everything else is the exact same and you can achieve all that and more with aftermarket parts discussed above.
Q. Do I need to do coil-overs, 98% street car?
Bottom line, No. No one needs them but I strongly recommend them. If for no other reason than you can have a high wheel rate with a lower spring rate. What that all means is you can install a spring that is half as stiff in the front and three fourths as stiff in the rear in a coil overs configuration as opposed to a standard configuration and still have better performance. By increasing the spring’s mechanical advantage you increase its effectiveness and reduce NVH. Not to mention reduced weight, ride height adjustability and you can swap springs much easier if you want to change spring rates.
Q. What should I do to the front end of my car to make it handle better?
The front end of a mustang is fairly simple. A basic outline is as follows.
Budget = shocks, springs, caster camber plates, bump steer kit, x2 ball joints and aluminum rack bushings.
Mid-Range = coil-overs, caster camber plates, bump steer kit, x2 ball joints and aluminum rack bushings.
Hi-End = Tubular K member & A arms, coil-overs, caster camber plates, bump steer kit and aluminum rack bushings.
Now your best bet is to call up Griggs Racing or Maximum Motorsports and discuss your goals with them and they will gladly assist you.
Q. What settings should I align my car to?
To answer this question you should understand what each setting is and what it does. I would you recommend you read this article first. Below are my alignment settings. Now realize that they are very aggressive but I did that for a reason.
_______Alignment Settings______
_______________Left______Right
Front Camber___-2.33°____-2.33°
Front Caster____+6.50°___+7.00°
Front Toe______+0.01"____+0.01"
Rear Camber____-0.75°____-0.75°
Rear Toe_______+0.05"____+0.05"
First off you want to get as much front caster as possible so have the technician set that at the limit of the adjustment range (if you have a bump steer kit). You may want to keep them equal if you drive on very flat roads. Here in Nebraska most roads have a very pronounced crown to aid in drainage of rain and snow so I have half a degree of cross caster to keep the car from pulling toward the passenger side. If you live in a place like Arizona where there is no precipitation and the roads are virtually flat you probably want to keep them even. Now my front camber setting is also quite aggressive. Unless you have an aftermarket suspension (K member, A arms, bump steer kit, etc.) you will probably want to keep yours around 0.1° negative. Now front toe depends on how much caster you run because the more caster you are able to get the less toe you will need to keep the car going straight without having to constantly correct the wheel whenever you encounter an irregularity on the road. So if you are able to set a high positive caster like I am you will be able to reduce your toe and consequently reduce your tire wear. If not then I would stick with the factory setting of .5° toe-in. (Notice the measurements for my toe settings are in inches not degrees.) As for the rear 0.75 degrees negative camber will put a little more weight on the inside edge of the tire but not a lot and based on what I have seen on a few IRS camber curves at stock ride height the camber goes further negative through droop and bump but when the car is lowered the camber goes positive as you droop just about until you would have been as stock ride height then begins going negative again. So that is the reasoning for me adding in a little negative camber to combat the positive camber gain through initial droop. So depending on your ride height and tire wear you may want to adjust this setting for your cars' characteristics. Basically if you are wearing the inside edge of the rears less negative rear camber is in order and conversely if the opposite is true more negative camber in the rear. Rear toe in is also largely dependent on what modifications you have done. Hopefully you have done a bump steer kit in the rear and if so your toe stays constant through the range of motion. I added a little rear toe in. This is because on a rear drive vehicle (with a positive offset wheel) the thrust of the rear wheels tends to pull them toward toe out and ideally you want zero toe in the rear so if you have just a little rear toe in the power of the car will pull the wheels in to a zero toe alignment and plus you would not want a toe out situation in the rear or the car would be all over the place under power.
------- Notes ------
Front Caster
Front caster can only be adjusted with aftermarket caster camber plates. I recommend Griggs, Maximum Motorsports and Steeda (the new 4 bolt design only).
Rear Camber
When the wheel is off the ground, and the upper knuckle is loose, the weight of it tends to rotate the wheel towards positive camber of course. Adjusting the eccentric to the max negative camber by rotating the bolt, only goes so far... the upper arm end is slotted on both sides to allow the bolt to adjust, and to get max camber out of it, it needs to be pushed back in the slot further on both sides of the bolt (The bolt will torque down at an angle if you let it, as the eccentric is on the opposite side).
Q. I am getting irregular tire wear what’s the deal?
It is most likely a factor of a few things. Your alignment settings have a lot to do with it (see above) and your tires must be properly inflated. Even if it looks fully inflated on the outside edge remember there is more weight on the inside edge because of negative camber so adding a few PSI may help. Your driving habits play an important part and unless you have modified your IRS as described above the compliance of your all the parts moving you never even keep your rear wheels in alignment under power and when she squats the camber goes even more negative. Finally if you are a real corner carver the stock diff leaves a lot to be desired in the twisties and causes some additional tire wear.
Q. I want to upgrade my sway bar where do I go?
Virtualy no one makes sway bar upgrades because the factory bar is very good. If you want to upgrade your handling the sway bar is the last place you need to mess with (unless you are talking about upgrading the bushings or end links).
=============== IRS Drop Instructions ================
1. Get car up on 4 jack stands with the tires about 8-10" off the ground
in the rear and 4-6" in the front. A little angle is important to keep
the trans from leaking when you pull out the driveshaft.
2. Remove catback. Soap or spray lube on the hangers ease insertion/removal.
3. Remove Driveshaft use 12pt 12mm socket. Pull it out of the trans.
4. Remove tires 13/16" socket.
5. Remove lower shock bolt. 18mm socket, disconnect bottom only, leave them hanging.
6. Remove ABS sensors from differential and pull/pry the fasteners off
the IRS subframe. Get it completely off the IRS. They detach under the
rear seats. You can pull up through the floor if you pull the big
rubber grommet up.
7. Remove Emergency brake cables. There are little c-clips mounting them
to the calipers. DO NOT remove the spring, way harder to get it back
together. Just push on the little arm holding the cable end till you
can work it out. I use vice grips to compress it. Make sure e-brake is
off, of course. Also have a helper pull all the slack to the side you
are working on.
8. Remove brake calipers, two 15mm bolts. Put jack underneath bottom of
spindle, just support it. Mark the position of the eccentric washer
where the UCA mounts to the top of the spindle. Remove upper
spindle/UCA bolt 18mm. Pull back on top of spindle and slip the brake line
out from under the UCA. Remove brake line bracket, 7mm bolt, which mounts to UCA. Replace the upper spindle bolt momentarily.
9. Remove rear IRS subframe bolts, 18mm. Support IRS at the center of the main
rear beam, directly rear of the pinion mount bracket (back of the
diff). Take both bolts out once it is supported. Use some 4x4's or
jack stands to support it a few inches under its normal position (you
don't want to lower it to ground till the front is loose.) You just
want to lower it enough so the springs will come out.
10. With the rear supported on 4x4's or jack stands, put the jack under
the front differential brace. Remove the front IRS subframe bolts.
Lower the front down. It may stick, both the ones I have done needed a
few smacks with a mallet. Once loose lower to the 4x4's then reposition
the jack, lift a bit, remove 4x4's and lower to ground or pull out from
under the car on top of the jack.
11. Reinstall in reverse order. Be sure to get it up close again on
4x4's, too much angle and the front bushings will not go in.
*CRITICAL that you install the FRONT first because those bolts have to go through fixed holes. The REAR bushing nuts (which are movable) and can be positioned to line up with the hole in the bushing. After the fronts are installed (and still a bit loose) swing up the rear, look through the hole, line up the nut behind it and insert the bolt.
Remember to swap out the stock 12mm front IRS bolts for the new 14mm bolts from
MM.
Q. Why shouldn’t I just swap in a solid axle rather than build my IRS?
If you choose to swap your IRS for a solid rear axel that is your decision but I believe you are making the wrong decision and Chuck Schwynoch of Maximum Motorsports agrees with me.
NASA Pro Racing – Interview with Chuck Schwynoch, CEO
Maximum Motorsports, Inc.
June 28, 2006
By Andy Bowman
Q. The #91 MM Mustang is using an IRS rear suspension, what drove you to this decision, how has the effort been going so far?
A. We had a growing number of customers who called us and said that they were not happy with their IRS, and asked us if they should swap in the proven MM Torque-arm/Panhard Bar rear suspension. We couldn't give them a truthful answer until we had done our own testing to directly compare the Ford IRS to a well-sorted Torque-arm/Panhard bar system. Our AI race car had won races, and set track records, so it was the perfect candidate for comparison. We swapped the rear end over to the IRS, with all of the parts we had developed over the previous year on a street-driven 2003 Cobra. We left the front of the car exactly as it was with the Torque arm suspension. We maintained the exact same rear track width, and even swapped over the same brakes, rotors, calipers, and pads, from the solid axle. We then hit the track for testing. By the end of the first day of testing we were 3 seconds under the AI track record at Buttonwillow. With the IRS we had to learn what alignment and bumpsteer settings worked best. That's what testing told us. Without track testing, we really could not have given our customers an honest answer to their questions about the IRS. Even if our testing had shown the IRS to be grossly inferior to a solid axle, we at least would then be able to help our customers make an informed decision about modifying their car. As it turned out, the IRS is superior to a solid axle fitted with a Torque-arm and Panhard bar, in most aspects. And he is speaking of a Torque-arm/Panhard bar built solid rear vs. a built IRS. A stock four link solid rear is a joke by comparison. If they race it competitively in a very demanding series and they are a suspension/race shop and they say it is faster and better in most ways I'd tend to believe them. Add that to the fact that every world class sports car has an independent suspension. I don't think SVT was trying to install an inferior suspension in the top line car.
Q. Isn’t building the IRS more expensive than a built solid axel?
No. For instance the Maximum Grip Box from Maximum Motorsports for the SRA costs MORE than the Maximum Grip Box for the IRS. So there goes that argument (as seen here). Not to mention that ac427cobra's bushing kit costs a fraction of what MM's do...
Q. Are the Install costs for a built IRS more than a torque arm/panhard rod SRA?
I can tell you that it costs more to weld parts on to a car and setup a new suspension than to replace bushings and bolt on a few parts for the IRS.
Q. Even with a built IRS as described above wont the IRS still break?
The only parts that can fail in the IRS once properly built as described above are the Diff (same as in a SRA) and the half shfts instead of the axles in a SRA. If you have a properly articulating suspension you will not break 03 half shafts unless you are running extreme power at the strip (and most aren't). If you are then yes you may want to look in to DSS shafts but 03 shafts are just as strong as stock SRA axles. Just because some uninformed people when out to the strip and broke some shafts before knowing that modifications were needed to prevent part breakage doesn't mean it is an inferior suspension. That is like saying the SRA is crap because some people ripped their torque boxes up. They didn't know that they needed to weld some bracing not the suspensions fault.
Q. The solid rear axel seems to be fine right out of the box why shouldn’t I just run that?
The SRA is a poorly designed suspension and that is well documented...
Taken from the Griggs Racing website
An even larger concern is found in the rear suspension. Ford uses a 4-link design, but with the upper two control arms angled heavily outward. This means the lower and upper rear control arms are not parallel, so as the suspension moves the upper arms are twisted in their bushings. During performance driving this quickly leads to a near total binding of the rear suspension, called roll bind. With the axle bound, it acts like a giant anti-sway bar, causing the rear roll stiffness to skyrocket and the overloaded rear tires to loose traction and spin. This is why the rear end snaps into uncontrollable fishtailing when cornering, and it is also why the rear tires break loose at the drag strip once the body starts rising from the initial power hit. And Griggs is a strong propionate of the Torque Arm, Panhard Bar SRA. I know Bruce Griggs personally and he and I have had discussions about the topic a few different times. He doesn't like the built IRS in comparison to a built SRA but one thing we completely agree on is that the Fox and SN95 SRAs are totally unacceptable as delivered from the factory. I run his front suspension and it is amazing, I also run a few of his rear parts but for the most part the rear of my car is a mix of parts all working together to create super car like handling and performance. Based on what can be saved on parts and labor costs, a built IRS is a cheaper, less labor intensive, and superior suspension in all cases to a built SRA (except dedicated drag race cars).
Q. Won’t the delrin bushing squeak eventually?
With grease fittings installed you should never have squeaking. All you have to is have a technician shoot some grease in to the joints every few oil changes and your done. I have had delrin bushings in my Griggs front control arms for years now and all I have to do is add some grease about every 2 years or so you can probably expect similar results in the IRS but your mileage may vary.
Q. Do I need level 5 half shafts?"
Most likely not, but it depends. The 1999 half shafts are really not sufficient for mildly to highly modded cars drag racing with slicks or DR's even after you remove all of the rubber preventing wheel hop. I say run them till you break them but you most likely will. Your best bet at that point would be to purchase better shafts from Raxles or upgrade to a 31 spline differential and install '03 half shafts. 01 owners face the same situation but would not need to upgrade the differential to run 03 half shafts. If you then break one of the '03 Ford half shafts, and you have already removed all of the rubber from your IRS assembly, you need to look at DSS shafts.
Q. What if I already broke a 03 half shaft?
If you have then it may be time to upgrade, but only if you've removed all of the rubber in your IRS assembly and still broke a half shaft. More half shafts have been broken due to wheel hop directly caused by the components mounted in rubber, than broken because of sheer power. Once all rubber is removed from the IRS assembly and you break a half shaft, then by all means you're a candidate for DSS shafts.
Q. What is bump steer?
Bumpsteer is the term for the situation when the toe angle of a wheel changes as the suspension moves up and down, such as when driving over bumps, or with body roll during cornering. This happens when the arc that the spindle travels during bump and droop is not the same as the arc of the outer tie-rod end. If the toe changes more than a very small amount, the rear wheels begin steering the car.
Q: "How important is bump steering the IRS?"
Bump steering the IRS is not required but highly recommended and you will notice a difference.
Q: "Why do I hear a clunk in my drivetrain?"
There are a few likely reasons for the clunk. Your transmission and gears can combine for quite a bit of play, but that usually is not the main source of the "clunk". A few different things can contribute to the Cobra "clunk". The most likely are the bushings the differential is mounted with. The rubber OEM differential bushings are soft and spongy. Defiantly not the kind of material I would select to mount a component that is expected to translate all the driveshaft’s rotational force to the half shafts. These soft bushings allow the differential to move and that clunk you hear is most likely that movement. The situation is even worse for 99/01 owners because the bushings for those years were even softer and Ford had not yet developed the differential support brace. See section E1 for further details.
An alternative reason could be the front subframe mounting bolts. On some 2003 and 2004 cobras Ford accidently installed 12mm bolts rather than 14mm bolts that allow the subframe to shift during acceleration and breaking and cornering. Larger bolts will remedy this situation see section E12.
Q. Wont the suspension be more noisy with all those solid bushings?
Yes and No. I didn't notice any additional vibration or harshness because any bumps or road irregularities are transmitted to the suspension rather than the car. The solid bushings in most locations should not add any NVH to your car but the solid bushings used to mount the differential will increase your cabin noise but nothing terrible and certainly not a deal breaker IMO. But as I said in my review the noise increase is equivalent to installing an aftermarket shifter without installing a shifter gasket or any noise canceling material. You just hear a little more gear whine from the differential after it is solidly mounted. If you are worried about it buy some Dynamat and you will be fine.
Q. I’ve heard that drag radials will cure my wheel hop, is that true?
They will help but that is far from a solution those that say buy some drag radials and you will be fine are wrong. Maybe if you drive like a grandmother then yes you don’t have wheel hop anymore but your recipe won’t work for the rest of us.
Q. Why does my IRS hop more now than it used to?
The suspension performs better when it is new because the rubber has yet to soften up and begin to deteriorate. This means they allow even more undesirable suspension movement.
Q. What is the difference between the 03/04 IRS and the 99/01 IRS?
From 99 the 01's had 31 spline diff and half shafts which was no real improvement as the spline count was not the problem. The 99 & 01 shafts taper down at the CV boot and create a weak point. The 03 Shafts are a constant diameter and are by comparison much stronger. The 03's also had stiffer bushings along with better shocks, stiffer springs, the addition of a forward differential pinion brace, and lower inner toe control mounting points. These improvements made it handle a little better, improved durability and reduced bump steer. Everything else is the exact same and you can achieve all that and more with aftermarket parts discussed above.
Q. Do I need to do coil-overs, 98% street car?
Bottom line, No. No one needs them but I strongly recommend them. If for no other reason than you can have a high wheel rate with a lower spring rate. What that all means is you can install a spring that is half as stiff in the front and three fourths as stiff in the rear in a coil overs configuration as opposed to a standard configuration and still have better performance. By increasing the spring’s mechanical advantage you increase its effectiveness and reduce NVH. Not to mention reduced weight, ride height adjustability and you can swap springs much easier if you want to change spring rates.
Q. What should I do to the front end of my car to make it handle better?
The front end of a mustang is fairly simple. A basic outline is as follows.
Budget = shocks, springs, caster camber plates, bump steer kit, x2 ball joints and aluminum rack bushings.
Mid-Range = coil-overs, caster camber plates, bump steer kit, x2 ball joints and aluminum rack bushings.
Hi-End = Tubular K member & A arms, coil-overs, caster camber plates, bump steer kit and aluminum rack bushings.
Now your best bet is to call up Griggs Racing or Maximum Motorsports and discuss your goals with them and they will gladly assist you.
Q. What settings should I align my car to?
To answer this question you should understand what each setting is and what it does. I would you recommend you read this article first. Below are my alignment settings. Now realize that they are very aggressive but I did that for a reason.
_______Alignment Settings______
_______________Left______Right
Front Camber___-2.33°____-2.33°
Front Caster____+6.50°___+7.00°
Front Toe______+0.01"____+0.01"
Rear Camber____-0.75°____-0.75°
Rear Toe_______+0.05"____+0.05"
First off you want to get as much front caster as possible so have the technician set that at the limit of the adjustment range (if you have a bump steer kit). You may want to keep them equal if you drive on very flat roads. Here in Nebraska most roads have a very pronounced crown to aid in drainage of rain and snow so I have half a degree of cross caster to keep the car from pulling toward the passenger side. If you live in a place like Arizona where there is no precipitation and the roads are virtually flat you probably want to keep them even. Now my front camber setting is also quite aggressive. Unless you have an aftermarket suspension (K member, A arms, bump steer kit, etc.) you will probably want to keep yours around 0.1° negative. Now front toe depends on how much caster you run because the more caster you are able to get the less toe you will need to keep the car going straight without having to constantly correct the wheel whenever you encounter an irregularity on the road. So if you are able to set a high positive caster like I am you will be able to reduce your toe and consequently reduce your tire wear. If not then I would stick with the factory setting of .5° toe-in. (Notice the measurements for my toe settings are in inches not degrees.) As for the rear 0.75 degrees negative camber will put a little more weight on the inside edge of the tire but not a lot and based on what I have seen on a few IRS camber curves at stock ride height the camber goes further negative through droop and bump but when the car is lowered the camber goes positive as you droop just about until you would have been as stock ride height then begins going negative again. So that is the reasoning for me adding in a little negative camber to combat the positive camber gain through initial droop. So depending on your ride height and tire wear you may want to adjust this setting for your cars' characteristics. Basically if you are wearing the inside edge of the rears less negative rear camber is in order and conversely if the opposite is true more negative camber in the rear. Rear toe in is also largely dependent on what modifications you have done. Hopefully you have done a bump steer kit in the rear and if so your toe stays constant through the range of motion. I added a little rear toe in. This is because on a rear drive vehicle (with a positive offset wheel) the thrust of the rear wheels tends to pull them toward toe out and ideally you want zero toe in the rear so if you have just a little rear toe in the power of the car will pull the wheels in to a zero toe alignment and plus you would not want a toe out situation in the rear or the car would be all over the place under power.
------- Notes ------
Front Caster
Front caster can only be adjusted with aftermarket caster camber plates. I recommend Griggs, Maximum Motorsports and Steeda (the new 4 bolt design only).
Rear Camber
When the wheel is off the ground, and the upper knuckle is loose, the weight of it tends to rotate the wheel towards positive camber of course. Adjusting the eccentric to the max negative camber by rotating the bolt, only goes so far... the upper arm end is slotted on both sides to allow the bolt to adjust, and to get max camber out of it, it needs to be pushed back in the slot further on both sides of the bolt (The bolt will torque down at an angle if you let it, as the eccentric is on the opposite side).
Q. I am getting irregular tire wear what’s the deal?
It is most likely a factor of a few things. Your alignment settings have a lot to do with it (see above) and your tires must be properly inflated. Even if it looks fully inflated on the outside edge remember there is more weight on the inside edge because of negative camber so adding a few PSI may help. Your driving habits play an important part and unless you have modified your IRS as described above the compliance of your all the parts moving you never even keep your rear wheels in alignment under power and when she squats the camber goes even more negative. Finally if you are a real corner carver the stock diff leaves a lot to be desired in the twisties and causes some additional tire wear.
Q. I want to upgrade my sway bar where do I go?
Virtualy no one makes sway bar upgrades because the factory bar is very good. If you want to upgrade your handling the sway bar is the last place you need to mess with (unless you are talking about upgrading the bushings or end links).
=============== IRS Drop Instructions ================
1. Get car up on 4 jack stands with the tires about 8-10" off the ground
in the rear and 4-6" in the front. A little angle is important to keep
the trans from leaking when you pull out the driveshaft.
2. Remove catback. Soap or spray lube on the hangers ease insertion/removal.
3. Remove Driveshaft use 12pt 12mm socket. Pull it out of the trans.
4. Remove tires 13/16" socket.
5. Remove lower shock bolt. 18mm socket, disconnect bottom only, leave them hanging.
6. Remove ABS sensors from differential and pull/pry the fasteners off
the IRS subframe. Get it completely off the IRS. They detach under the
rear seats. You can pull up through the floor if you pull the big
rubber grommet up.
7. Remove Emergency brake cables. There are little c-clips mounting them
to the calipers. DO NOT remove the spring, way harder to get it back
together. Just push on the little arm holding the cable end till you
can work it out. I use vice grips to compress it. Make sure e-brake is
off, of course. Also have a helper pull all the slack to the side you
are working on.
8. Remove brake calipers, two 15mm bolts. Put jack underneath bottom of
spindle, just support it. Mark the position of the eccentric washer
where the UCA mounts to the top of the spindle. Remove upper
spindle/UCA bolt 18mm. Pull back on top of spindle and slip the brake line
out from under the UCA. Remove brake line bracket, 7mm bolt, which mounts to UCA. Replace the upper spindle bolt momentarily.
9. Remove rear IRS subframe bolts, 18mm. Support IRS at the center of the main
rear beam, directly rear of the pinion mount bracket (back of the
diff). Take both bolts out once it is supported. Use some 4x4's or
jack stands to support it a few inches under its normal position (you
don't want to lower it to ground till the front is loose.) You just
want to lower it enough so the springs will come out.
10. With the rear supported on 4x4's or jack stands, put the jack under
the front differential brace. Remove the front IRS subframe bolts.
Lower the front down. It may stick, both the ones I have done needed a
few smacks with a mallet. Once loose lower to the 4x4's then reposition
the jack, lift a bit, remove 4x4's and lower to ground or pull out from
under the car on top of the jack.
11. Reinstall in reverse order. Be sure to get it up close again on
4x4's, too much angle and the front bushings will not go in.
*CRITICAL that you install the FRONT first because those bolts have to go through fixed holes. The REAR bushing nuts (which are movable) and can be positioned to line up with the hole in the bushing. After the fronts are installed (and still a bit loose) swing up the rear, look through the hole, line up the nut behind it and insert the bolt.
Remember to swap out the stock 12mm front IRS bolts for the new 14mm bolts from
MM.
01-21-2016, 02:02 PM
#7
5th Gear Member
Thread Starter
Join Date: May 2009
Location: kentucky
Posts: 2,241
IRS Tech
=============== Differential Removal ===============
1. Get car up on 4 jack stands with the tires about 8-10" off the ground
in the rear and 4-6" in the front. A little angle is important to keep
the trans from leaking when you pull out the driveshaft.
2. Remove catback. Soap or spray lube on the hangers ease insertion/removal.
3. Remove Driveshaft use 12pt 12mm socket. Pull it out of the trans.
4. Remove tires 13/16" socket.
5. Remove lower shock bolt. 18mm socket, disconnect bottom only, leave them hanging.
6. Remove Emergency brake cables. There are little c-clips mounting them to the calipers. Make sure e-brake is
off, of course. Also have a helper pull all the slack to the side you are working on. DO NOT remove the spring, way harder to get it back together. Just push on the little arm holding the cable end till you can work it out. I use vice grips to compress it.
7. Disconnect ABS sensors from diff T40 torx or 1/2" wrench.
8. Remove brake calipers, two 15mm bolts. Use some coat hanger wire or zip ties and hang them from the IRS mount bracket or anywhere out of the way.
9. Disconnect Toe Link Bar from spindle. Pull out cotter pin. Remove castle nut 18mm. DO NOT HIT the taper bolt with a hammer; you will crush it because of the cotter pin hole. You can either use a tie rod puller (AutoZone 25202 3.5") or the pry bar way. Spray taper bolt with penetrating oil, use long screwdriver or prybar and apply downward force on the cast end of the bar while striking the rearmost point on the spindle. Pry downward and hit it hard, it will come out.
10. Remove half shaft/spindle assy.
Put jack underneath bottom of spindle where it meets LCA, just support it. Mark the position of the eccentric washer on the Camber Bolt where the UCA mounts to the top of the spindle. You will realign these marks during reassembly to maintain current suspension setting. Forgetting to do this will mess up your tires and ride feel.
Remove upper spindle/UCA bolt 18mm.
Lower jack all the way down allowing the springs to stretch out. Remove jack.
Remove lower spindle/LCA bolt 18mm.
Pull half shaft out about 1/2"
Use flat screwdriver/prybar between diff and inner hub to make sure it is coming out of the diff. Pull half shaft all the way out.
Repeat for the other side.
11. Remove two 18mm bolts from diff cover-to-rear bushing. Leaves the rear diff bushing bracket hanging momentarily while we proceed to get the diff out.
12. Remove Front Differential bushing bolts 15mm
13. Remove nuts off front (only) LCA pivot bolts 24mm. Leave the bolts in place though. This allows the front differential support brace to be removed.
14. Remove Diff. Support rear of diff with a jack, remove front support brace and diff will move forward and down and out of the car. It is about 70lbs so be careful. Do not tip it or you will spill "fish guts" the nastiest smelling oil there is.
15. Remove Rear Differential bushing bracket bolt. 15mm and lots of extensions from the drivers side. Very tough to get to initially. Easier if you also remove drivers side toe link bar from its inner mounting point 13mm bolt on bottom, 15mm nut above.
Good time to reseal the diff with Permatex Ultra Grey ($4 Autozone) or Ford TA31 Diesel Sealant ($15 dealer only)
=============== Torque Specs ===============
IRS TORQUE SPECS
Subframe-to-body bolts 76 lb-ft
Subframe-to-rear bracket bolts 76 lb-ft
Subframe rear bracket-to-body bolts 59 lb-ft
Shock absorber-to-lower arm and bushing bolts 98 lb-ft
Shock absorber-to-body nuts 30 lb-ft
Upper arm and bushing-to-subframe nuts 66 lb-ft
Upper arm bushing-to-knuckle nut 66 lb-ft
Lower arm and bushing-to-subframe bolts 184 lb-ft
Lower arm and bushing-to-knuckle nut 85 lb-ft
Toe link-to-subframe nut 35 lb-ft
Toe link-to-knuckle nut 35 lb-ft
Stabilizer bar bracket bolt 41 lb-ft
Stabilizer bar link nuts 35 lb-ft
Rear axle diff rear insulator-to-axle housing bolts 76 lb-ft
Rear brake disc dust sheild-to-knuckle bolts 89 lb-in
Brake line-to-rear brake caliper bolt 30 lb-ft
Parking brake cable bracket-to-lower arm bushing bolt 11 lb-ft
ABS sensor bolt 17 lb-ft
Axle shaft-to-hub retainer 240 lb-ft
Driveshaft to pinion flange 83 lb-ft
Wheel nuts 95 lb-ft
FRONT END TORQUE SPECS
Front shock absorber upper nut - 74 ft/lbs
Front shock absorber-to-spindle nuts - 148 ft/lbs
Shock absorber upper mount-to-body nuts - 30 ft/lbs
Shock absorber upper mount-to-body bolt - 30 ft/lbs
Wheel hub and bearing retainer nut - 258 ft/lbs
Stabilizer bar bracket nuts - 52 ft/lbs
Stabilizer bar link nuts - 14 ft/lbs
Anti-lock brake sensor bolt - 53 in/lbs
Anti-lock brake sensor wire bracket nut - 21 ft/lbs
Ball joint-to-front wheel spindle nut - 129 ft/lbs
Front suspension lower arm-to-body nuts - 148 ft/lbs
Tie-rod-to-spindle nuts - 41 ft/lbs
Steering gear-to-crossmember nuts - 52 ft/lbs
Wheel nuts - 95 ft/lbs
=============== Step by Step Transmission Removal ===============
1. Disconnect Battery
2. Get car up on jack stands, tall ones, need 12" under the tires airspace
3. Remove Shifter handle, bezel/plate and then shifter.
4. Remove mid pipe
5. Remove driveshaft (use a trans plug or towel to keep the tail shaft from leaking, or drain it).
6. Remove Trans mount
7. Unplug all electrical connections from the trans
8. Remove clutch inspection cover
9. Detach clutch cable
10. Remove lower 4 trans bolts
11. Support with trans jack
12. Remove remaining upper trans bolts
13. Slide trans back and lower trans jack down
=============== Useful links ===============
AC427Cobra’s Informational Videos:
http://fulltiltboogieracing.com/info...nal_videos.htm
Postban's IRS build up article along with IRS drop procedure and torque specs can be found here:
http://www.svtperformance.com/forums...d.php?t=231900
A good mustang suspension article:
http://www.miracerros.com/mustang/t_suspension.htm
A very good post about mounting larger wheels and tires on an IRS cobra.
http://www.svtperformance.com/forums...4&postcount=16
A nice article about driveline alignment (no more 80 MPH vibe).
http://home.flash.net/~ivc1/cobra/irsvibes.html
1. Get car up on 4 jack stands with the tires about 8-10" off the ground
in the rear and 4-6" in the front. A little angle is important to keep
the trans from leaking when you pull out the driveshaft.
2. Remove catback. Soap or spray lube on the hangers ease insertion/removal.
3. Remove Driveshaft use 12pt 12mm socket. Pull it out of the trans.
4. Remove tires 13/16" socket.
5. Remove lower shock bolt. 18mm socket, disconnect bottom only, leave them hanging.
6. Remove Emergency brake cables. There are little c-clips mounting them to the calipers. Make sure e-brake is
off, of course. Also have a helper pull all the slack to the side you are working on. DO NOT remove the spring, way harder to get it back together. Just push on the little arm holding the cable end till you can work it out. I use vice grips to compress it.
7. Disconnect ABS sensors from diff T40 torx or 1/2" wrench.
8. Remove brake calipers, two 15mm bolts. Use some coat hanger wire or zip ties and hang them from the IRS mount bracket or anywhere out of the way.
9. Disconnect Toe Link Bar from spindle. Pull out cotter pin. Remove castle nut 18mm. DO NOT HIT the taper bolt with a hammer; you will crush it because of the cotter pin hole. You can either use a tie rod puller (AutoZone 25202 3.5") or the pry bar way. Spray taper bolt with penetrating oil, use long screwdriver or prybar and apply downward force on the cast end of the bar while striking the rearmost point on the spindle. Pry downward and hit it hard, it will come out.
10. Remove half shaft/spindle assy.
Put jack underneath bottom of spindle where it meets LCA, just support it. Mark the position of the eccentric washer on the Camber Bolt where the UCA mounts to the top of the spindle. You will realign these marks during reassembly to maintain current suspension setting. Forgetting to do this will mess up your tires and ride feel.
Remove upper spindle/UCA bolt 18mm.
Lower jack all the way down allowing the springs to stretch out. Remove jack.
Remove lower spindle/LCA bolt 18mm.
Pull half shaft out about 1/2"
Use flat screwdriver/prybar between diff and inner hub to make sure it is coming out of the diff. Pull half shaft all the way out.
Repeat for the other side.
11. Remove two 18mm bolts from diff cover-to-rear bushing. Leaves the rear diff bushing bracket hanging momentarily while we proceed to get the diff out.
12. Remove Front Differential bushing bolts 15mm
13. Remove nuts off front (only) LCA pivot bolts 24mm. Leave the bolts in place though. This allows the front differential support brace to be removed.
14. Remove Diff. Support rear of diff with a jack, remove front support brace and diff will move forward and down and out of the car. It is about 70lbs so be careful. Do not tip it or you will spill "fish guts" the nastiest smelling oil there is.
15. Remove Rear Differential bushing bracket bolt. 15mm and lots of extensions from the drivers side. Very tough to get to initially. Easier if you also remove drivers side toe link bar from its inner mounting point 13mm bolt on bottom, 15mm nut above.
Good time to reseal the diff with Permatex Ultra Grey ($4 Autozone) or Ford TA31 Diesel Sealant ($15 dealer only)
=============== Torque Specs ===============
IRS TORQUE SPECS
Subframe-to-body bolts 76 lb-ft
Subframe-to-rear bracket bolts 76 lb-ft
Subframe rear bracket-to-body bolts 59 lb-ft
Shock absorber-to-lower arm and bushing bolts 98 lb-ft
Shock absorber-to-body nuts 30 lb-ft
Upper arm and bushing-to-subframe nuts 66 lb-ft
Upper arm bushing-to-knuckle nut 66 lb-ft
Lower arm and bushing-to-subframe bolts 184 lb-ft
Lower arm and bushing-to-knuckle nut 85 lb-ft
Toe link-to-subframe nut 35 lb-ft
Toe link-to-knuckle nut 35 lb-ft
Stabilizer bar bracket bolt 41 lb-ft
Stabilizer bar link nuts 35 lb-ft
Rear axle diff rear insulator-to-axle housing bolts 76 lb-ft
Rear brake disc dust sheild-to-knuckle bolts 89 lb-in
Brake line-to-rear brake caliper bolt 30 lb-ft
Parking brake cable bracket-to-lower arm bushing bolt 11 lb-ft
ABS sensor bolt 17 lb-ft
Axle shaft-to-hub retainer 240 lb-ft
Driveshaft to pinion flange 83 lb-ft
Wheel nuts 95 lb-ft
FRONT END TORQUE SPECS
Front shock absorber upper nut - 74 ft/lbs
Front shock absorber-to-spindle nuts - 148 ft/lbs
Shock absorber upper mount-to-body nuts - 30 ft/lbs
Shock absorber upper mount-to-body bolt - 30 ft/lbs
Wheel hub and bearing retainer nut - 258 ft/lbs
Stabilizer bar bracket nuts - 52 ft/lbs
Stabilizer bar link nuts - 14 ft/lbs
Anti-lock brake sensor bolt - 53 in/lbs
Anti-lock brake sensor wire bracket nut - 21 ft/lbs
Ball joint-to-front wheel spindle nut - 129 ft/lbs
Front suspension lower arm-to-body nuts - 148 ft/lbs
Tie-rod-to-spindle nuts - 41 ft/lbs
Steering gear-to-crossmember nuts - 52 ft/lbs
Wheel nuts - 95 ft/lbs
=============== Step by Step Transmission Removal ===============
1. Disconnect Battery
2. Get car up on jack stands, tall ones, need 12" under the tires airspace
3. Remove Shifter handle, bezel/plate and then shifter.
4. Remove mid pipe
5. Remove driveshaft (use a trans plug or towel to keep the tail shaft from leaking, or drain it).
6. Remove Trans mount
7. Unplug all electrical connections from the trans
8. Remove clutch inspection cover
9. Detach clutch cable
10. Remove lower 4 trans bolts
11. Support with trans jack
12. Remove remaining upper trans bolts
13. Slide trans back and lower trans jack down
=============== Useful links ===============
AC427Cobra’s Informational Videos:
http://fulltiltboogieracing.com/info...nal_videos.htm
Postban's IRS build up article along with IRS drop procedure and torque specs can be found here:
http://www.svtperformance.com/forums...d.php?t=231900
A good mustang suspension article:
http://www.miracerros.com/mustang/t_suspension.htm
A very good post about mounting larger wheels and tires on an IRS cobra.
http://www.svtperformance.com/forums...4&postcount=16
A nice article about driveline alignment (no more 80 MPH vibe).
http://home.flash.net/~ivc1/cobra/irsvibes.html
01-21-2016, 02:09 PM
#8
5th Gear Member
Thread Starter
Join Date: May 2009
Location: kentucky
Posts: 2,241
DIY Cool Suit ice box for dummies
link has pics
http://www.trackhq.com/forums/f195/d...-ice-box-3260/
doing this writeup, because when I Googled, few posts I've seen were not approved for dummies
edit: I've built 6 so far, all are still working in the team.
I spent about $100 total. build takes only 15 minutes, but finding correct parts was time consuming. so I thought this might help others. pretty sure you can build this for less and better. I am not that handy. I get lost in Home Depot.
tool:
1" hole saw
silicon adhesive
teflon tape
here are the parts you need:
dry breaks:
5/16" hose barb valved in-line coupling x 2
PLCD17005 - 5/16 Hose Barb Valved In-Line CPC Coupling Body
option:
5/16" hose barb non-valve x 1 - you need 1 of these so you can drain the water out of ice chest at end of day. because all connector are valved (closed), this un-valves (open) it. it can also be used to prime the pump (by sucking on it !!).
PLC22005 - 5/16 Hose Barb Non-valved In-Line CPC Coupling Insert
- 3/4" x 3" threaded PVC pipe x 2
- 3/4" ID vinyl tubing, 1.5FT long
- female hose nut to hose barb 5/8" x 3/4" x 1
- 5/16" ID vinyl tubing, 14FT long (length depends, this is for an ice box sitting in front passenger seat)
- 1" x 3/4" PVC bushing - this really is just to be used as a nut. for the 1st item above.
- female hose to hose barb swivel, 3/4" x 3/8" x 2. (this item was $7 at Lowes/HD, yet $2 at Osh).
- bilge pump x 1 - cheaper the better. the big one flows too much.
Walmart.com: Tsunami 500 GPH Cartridge Bilge Pump, 12VDC: Fishing & Boating
Amazon.com : Attwood Tsunami Manual Bilge Pump : Boating Bilge Pumps : Sports & Outdoors
- cooler - your choice. I have a 25qt (or 28qt) one, this is much bigger than commercial ones. reason: in SOCAL, we only drive in desert tracks. I also plan to use it in 6 hours enduro. it fit a 20LB ice you buy at gas stations. in 100F desert weather, it last a day (6 sessions) easily. important: buy a cooler (see blue one below) that has a continuous flat lid edge surface you can stick on insulation weatherstripping. the red cooler below can't do that, and will leak under cornering load next to the hinges.
edit: I buy this one now. it is lower profile. fit trunk better. $20 at Walmart.
Igloo Marine 25-quart cooler - Walmart.com
- insulation weatherstripping, to seal cooler lid. I bought the thinnest ones, but I've also tried thicker ones, no problem.
- noodle, 6ft - for insulating 5/16" vinyl tubing from cooler to suit.
- few hose clamps - don't really need it, but for a piece of mind.
notes:
- imo, it is better to mount the bilge pump toward front of the car. Braking G. is always higher than acceleration G (if don't own a supercar). it is also a good idea to tilt ever slightly, so pump is sitting at lowest point.
- solid block of ice lasts longer than crushed ice.
- you need a little bit of water to get the pump started.
- as for priming the pump. I still haven't got that down to science. once in a while (usually 1st time in morning), I will stick in one of the above non-valved dry break and use it to suck some water as to prime the pump.
- it is cheaper to buy nylon vs. brass parts (expensive) on few of items I've listed above. I was just too lazy to look for it. edit: Osh's parts were a lot cheaper (than Lowes or HD) for some reason. you probably save $20 or so.
- I did not screw/glue down the bilge pump. G. load helps it to go with the G. load is (where water are). works great.
- other than dry breaks bought online. bilge pump and cooler were bought in Walmart (or Amazon). everything else were from Lowes.
- ran the bilge pump wires through the lid opening. no leaks.
- install a switch to turn pump on and off.
- you might want to consider putting in a little of anti-fungal stuff, humid is not a good thing.
Mounts:
old way: I used my old factory passenger seat mounts, and strap the ice box down. it is very sturdy. new way: you can also use 2 flat aluminum bars (each bar screwed into seat mounting holes. and use that to strap the ice box.
Attached Thumbnails Attached Thumbnails 1.jpg 3.jpg
2.jpg 4.jpg
5.jpg 7.jpg
8.jpg 9.jpg
10.jpg 11.jpg
http://www.trackhq.com/forums/f195/d...-ice-box-3260/
doing this writeup, because when I Googled, few posts I've seen were not approved for dummies
edit: I've built 6 so far, all are still working in the team.
I spent about $100 total. build takes only 15 minutes, but finding correct parts was time consuming. so I thought this might help others. pretty sure you can build this for less and better. I am not that handy. I get lost in Home Depot.
tool:
1" hole saw
silicon adhesive
teflon tape
here are the parts you need:
dry breaks:
5/16" hose barb valved in-line coupling x 2
PLCD17005 - 5/16 Hose Barb Valved In-Line CPC Coupling Body
option:
5/16" hose barb non-valve x 1 - you need 1 of these so you can drain the water out of ice chest at end of day. because all connector are valved (closed), this un-valves (open) it. it can also be used to prime the pump (by sucking on it !!).
PLC22005 - 5/16 Hose Barb Non-valved In-Line CPC Coupling Insert
- 3/4" x 3" threaded PVC pipe x 2
- 3/4" ID vinyl tubing, 1.5FT long
- female hose nut to hose barb 5/8" x 3/4" x 1
- 5/16" ID vinyl tubing, 14FT long (length depends, this is for an ice box sitting in front passenger seat)
- 1" x 3/4" PVC bushing - this really is just to be used as a nut. for the 1st item above.
- female hose to hose barb swivel, 3/4" x 3/8" x 2. (this item was $7 at Lowes/HD, yet $2 at Osh).
- bilge pump x 1 - cheaper the better. the big one flows too much.
Walmart.com: Tsunami 500 GPH Cartridge Bilge Pump, 12VDC: Fishing & Boating
Amazon.com : Attwood Tsunami Manual Bilge Pump : Boating Bilge Pumps : Sports & Outdoors
- cooler - your choice. I have a 25qt (or 28qt) one, this is much bigger than commercial ones. reason: in SOCAL, we only drive in desert tracks. I also plan to use it in 6 hours enduro. it fit a 20LB ice you buy at gas stations. in 100F desert weather, it last a day (6 sessions) easily. important: buy a cooler (see blue one below) that has a continuous flat lid edge surface you can stick on insulation weatherstripping. the red cooler below can't do that, and will leak under cornering load next to the hinges.
edit: I buy this one now. it is lower profile. fit trunk better. $20 at Walmart.
Igloo Marine 25-quart cooler - Walmart.com
- insulation weatherstripping, to seal cooler lid. I bought the thinnest ones, but I've also tried thicker ones, no problem.
- noodle, 6ft - for insulating 5/16" vinyl tubing from cooler to suit.
- few hose clamps - don't really need it, but for a piece of mind.
notes:
- imo, it is better to mount the bilge pump toward front of the car. Braking G. is always higher than acceleration G (if don't own a supercar). it is also a good idea to tilt ever slightly, so pump is sitting at lowest point.
- solid block of ice lasts longer than crushed ice.
- you need a little bit of water to get the pump started.
- as for priming the pump. I still haven't got that down to science. once in a while (usually 1st time in morning), I will stick in one of the above non-valved dry break and use it to suck some water as to prime the pump.
- it is cheaper to buy nylon vs. brass parts (expensive) on few of items I've listed above. I was just too lazy to look for it. edit: Osh's parts were a lot cheaper (than Lowes or HD) for some reason. you probably save $20 or so.
- I did not screw/glue down the bilge pump. G. load helps it to go with the G. load is (where water are). works great.
- other than dry breaks bought online. bilge pump and cooler were bought in Walmart (or Amazon). everything else were from Lowes.
- ran the bilge pump wires through the lid opening. no leaks.
- install a switch to turn pump on and off.
- you might want to consider putting in a little of anti-fungal stuff, humid is not a good thing.
Mounts:
old way: I used my old factory passenger seat mounts, and strap the ice box down. it is very sturdy. new way: you can also use 2 flat aluminum bars (each bar screwed into seat mounting holes. and use that to strap the ice box.
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01-21-2016, 02:25 PM
#9
5th Gear Member
Thread Starter
Join Date: May 2009
Location: kentucky
Posts: 2,241
17x10" wide front wheel how to
Ill try and add my finding over my course of stuffing a 10 inch wheel up front. It can be done with a little fender rolling/pulling. As long as there is at least 6.360 of backspace, the wheel will clear the strut no matter if its 8,9 or 10 wide. I personally run the longer wheel studs so if I need say a 1/2 spacer, I can just buy a hubcentric spacer and go. If I think of anything else, ill add it in later.
This guy used the Enkei 17x10 wheel with 18mm offset, which is about 6.084 backspace
http://forums.corral.net/forums/road...1-brembos.html
Don't know the wheel brand but 17x10 with 25mm offset, 6.360 backspace
18x10 +25 all around, 275/35 front, 295/35 rear , 1/4" rear spacer
XXR 521 Wheels - Forums at Modded Mustangs
http://www.moddedmustangs.com/forums...21-wheels.html
OE wheels 95 R replicas 17x10.5 +27 offset on all fours with 5/16" spacer on front. PBR Cobra Brakes (post 8)
W I D E Front 17" wheels
http://forums.corral.net/forums/road...17-wheels.html
good info
http://forums.corral.net/forums/road...5-40-17-a.html
315s On All Four Corners
There seems to be some interest in this and I'd rather not take over another guy's thread, so:
I run a 1997 GT in E Street Prepared. The car has a torque arm, PHB, c/c plates, big springs, MM adjustable rear sway bar, Koni S/As in front and MM race-valved Bil's in the rear, near stock SOHC engine.
I was running 275's on 9 1/2" wide Borbet wheels; first VictoRacers and then 710s. The 710s were a big improvement over the VictoRacers and lasted longer, too! But, I wanted even more grip (who doesn't).
So, I decided to try and fit 315 Kumho 710s. I already had two 10 1/2" wide R replica wheels so I ordered two more. Now, these are heavy suckers at about 32# each and really 315s should be on 11-12" wide rims, but the R replicas are cheap. All four wheels have 7" back spacing.
In the rear I added a Maximum Motorsports 1/4" wheel spacer. This allows enough thread engagement with stock lug studs, but when I R&R the rear end, I will go to longer studs. I rolled the rear fender lips with the Eastwood tool. The tool works well, but even though I was pretty careful and used a heatgun, the paint cracked where the bend is - doesn't show, but you can feel it if you run your fingers along the fender edge. Oh well. The tires will rub on the inner fender ever so slightly entering a driveway at an angle or hitting a dip in a turn at an auto-cross. No harm, no foul.
The front was a little more involved. Since I knew I would need more than a 1/4" spacer, I got longer lugs. This were from MM and are a press fit. They cast about $8.00 each. Yes, each. You can get much cheaper ones from Moroso or ARP, but they are larger diameter and you must ream the holes in the hub.
Since I was going to have to take off the hubs to fit the new lug studs, and since the car has circa 75,000 miles and about 4 years of auto-crossing on it, I got new front hubs. About $75.00 each IIRC.
Then, I ordered 1/2" hubcentric wheel spacers from MM. And I odered an assortment of steering rack limiters from Ford. These come in several sizes and are needed to limit steering lock or the tire will rub on the front sway bar and the wheel (!) will rub on the rear of the front lower control arm at full lock. I used the 1/4" ones. The aleady large turning radius is a fair amount larger, but it's just fine for auto-cross. Tight parking manuevers need to be planned ahead, though.
Finally, I rolled the front fender lips, again with the Eastwood tool with the same results. I rolled the fronts farther than the rears and the formerly horizontal lip is now vertical and almost touches the fender. Oh yeah, the plastic fender liners are history. Hey, 5# off the front end and class legal as of this year.
NOTE: Others have used 6 1/4" back spacing (right, Glenn?) with good results, but a total of 6 1/2" front and 6 3/4' rear is what worked for me. YMMV.
Result - everthing fits and nothing rubs, except the rear inner fender as noted above. The front tires stick out a bit past the fender edge, maybe 1/8". But note that I have -3.2 degrees camber and 1300# springs in front. This almost certainly won't work with stock springs and camber.
In competition, I am right there with the other half-fast guys (the National champion caliber guy is still out front, but then, he's got 150 more rwhp and is a better driver). Turn in is noticeably less crisp (even with 3/8" total toe out), but front grip is much improved. Rear grip out of corners is better too, but with maybe 200 rwhp, wasn't a big problem anyway. The car will still pivot nicely when called upon. I haven't tried changing the rear sway bar setting yet. I did discover this setup likes lower tire pressure than I am used to - 28 psi front and 25 psi rear seems pretty close.
BTW, Gearing hasn't changed as the diameter of the 315's is almost identical to the 275s.
All-in-all, I am pretty happy with the results.
This guy used the Enkei 17x10 wheel with 18mm offset, which is about 6.084 backspace
http://forums.corral.net/forums/road...1-brembos.html
Don't know the wheel brand but 17x10 with 25mm offset, 6.360 backspace
18x10 +25 all around, 275/35 front, 295/35 rear , 1/4" rear spacer
XXR 521 Wheels - Forums at Modded Mustangs
http://www.moddedmustangs.com/forums...21-wheels.html
OE wheels 95 R replicas 17x10.5 +27 offset on all fours with 5/16" spacer on front. PBR Cobra Brakes (post 8)
W I D E Front 17" wheels
http://forums.corral.net/forums/road...17-wheels.html
good info
http://forums.corral.net/forums/road...5-40-17-a.html
315s On All Four Corners
There seems to be some interest in this and I'd rather not take over another guy's thread, so:
I run a 1997 GT in E Street Prepared. The car has a torque arm, PHB, c/c plates, big springs, MM adjustable rear sway bar, Koni S/As in front and MM race-valved Bil's in the rear, near stock SOHC engine.
I was running 275's on 9 1/2" wide Borbet wheels; first VictoRacers and then 710s. The 710s were a big improvement over the VictoRacers and lasted longer, too! But, I wanted even more grip (who doesn't).
So, I decided to try and fit 315 Kumho 710s. I already had two 10 1/2" wide R replica wheels so I ordered two more. Now, these are heavy suckers at about 32# each and really 315s should be on 11-12" wide rims, but the R replicas are cheap. All four wheels have 7" back spacing.
In the rear I added a Maximum Motorsports 1/4" wheel spacer. This allows enough thread engagement with stock lug studs, but when I R&R the rear end, I will go to longer studs. I rolled the rear fender lips with the Eastwood tool. The tool works well, but even though I was pretty careful and used a heatgun, the paint cracked where the bend is - doesn't show, but you can feel it if you run your fingers along the fender edge. Oh well. The tires will rub on the inner fender ever so slightly entering a driveway at an angle or hitting a dip in a turn at an auto-cross. No harm, no foul.
The front was a little more involved. Since I knew I would need more than a 1/4" spacer, I got longer lugs. This were from MM and are a press fit. They cast about $8.00 each. Yes, each. You can get much cheaper ones from Moroso or ARP, but they are larger diameter and you must ream the holes in the hub.
Since I was going to have to take off the hubs to fit the new lug studs, and since the car has circa 75,000 miles and about 4 years of auto-crossing on it, I got new front hubs. About $75.00 each IIRC.
Then, I ordered 1/2" hubcentric wheel spacers from MM. And I odered an assortment of steering rack limiters from Ford. These come in several sizes and are needed to limit steering lock or the tire will rub on the front sway bar and the wheel (!) will rub on the rear of the front lower control arm at full lock. I used the 1/4" ones. The aleady large turning radius is a fair amount larger, but it's just fine for auto-cross. Tight parking manuevers need to be planned ahead, though.
Finally, I rolled the front fender lips, again with the Eastwood tool with the same results. I rolled the fronts farther than the rears and the formerly horizontal lip is now vertical and almost touches the fender. Oh yeah, the plastic fender liners are history. Hey, 5# off the front end and class legal as of this year.
NOTE: Others have used 6 1/4" back spacing (right, Glenn?) with good results, but a total of 6 1/2" front and 6 3/4' rear is what worked for me. YMMV.
Result - everthing fits and nothing rubs, except the rear inner fender as noted above. The front tires stick out a bit past the fender edge, maybe 1/8". But note that I have -3.2 degrees camber and 1300# springs in front. This almost certainly won't work with stock springs and camber.
In competition, I am right there with the other half-fast guys (the National champion caliber guy is still out front, but then, he's got 150 more rwhp and is a better driver). Turn in is noticeably less crisp (even with 3/8" total toe out), but front grip is much improved. Rear grip out of corners is better too, but with maybe 200 rwhp, wasn't a big problem anyway. The car will still pivot nicely when called upon. I haven't tried changing the rear sway bar setting yet. I did discover this setup likes lower tire pressure than I am used to - 28 psi front and 25 psi rear seems pretty close.
BTW, Gearing hasn't changed as the diameter of the 315's is almost identical to the 275s.
All-in-all, I am pretty happy with the results.
Last edited by school boy; 01-25-2016 at 04:48 PM.
01-21-2016, 02:29 PM
#10
5th Gear Member
Thread Starter
Join Date: May 2009
Location: kentucky
Posts: 2,241
Functionl Hood Vent
http://forums.corral.net/forums/road...ood-vents.html
This link has several different years of mustangs and discusses the use and install of a functional hood vent. Good info for open track cars!
This link has several different years of mustangs and discusses the use and install of a functional hood vent. Good info for open track cars!