Upgrade brakes ~ Speeding up slowing down

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12-08-2010, 09:21 PM

Jazzer The Cat

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Join Date: Jun 2006

Location: SF Bay Area

Posts: 9,235

Upgrade brakes ~ Speeding up slowing down

I was hoping to have the aid of my Bernie Taupin to your Elton John, that being The Good ReverendDexter, but have not heard from him with some write-ups

He is far better versed in braking than I, but without my golden pipes, this thread might look like a golden stream

I feel this thead may grow quite long and probably frustrate those who seek it out for his/her questions.

... but first, all the legal crappola to keep my *** from getting sued

DISCLAIMER:

You will find good/useful information, but will not be as informative today, as it will be going forward. I will continue to edit/add/correct/provide information as much as needed to help my pepes out with questions regarding brakes. Furthermore, this is a GENERAL guide for the improvement of braking on your Mustang. There is much more to a well designed brake system, such as for race and open-track cars and will not be getting into all of this. In most cases, the OEM brakes are going to be fine, but will likely prove to be inadequate on a high-performance Mustang. In my opinion, this would include anyone who drives even modestly more aggressive than your grandma

This would certainly include those who have done mods to improve horse-power/torque output of ones engine. If you have done this, you WILL exceed the speed limit at some point and will need to stop at another

$350 to stop the madness!

OEM GT calipers, OEM GT rotors and.......
Good pads, but not limited to:
Brembo
Hawk ~ HPS up front is what I run. No noise, minimal dust, but is a subjective opinion
Porterfield
Wilwood
Stainless-Steel lines:
Fronts & rears ~ MM has fronts, AM has fronts/rears
Fluid:
DOT5.1 or better ~ It is not any more substantial amount of money for the "good stuff", so why not go race quality? (see brake fluid below)
.... for spectacular brakes that are better* than an factory Cobra! That's it.... hit up some websites and order your parts, because all that is left is waiting for your parts and an afternoon of help from your buddy :stickpoke If you are into the esthetics, or just want larger cross-drilled and/or slotted rotors, read on my friend....

*better ~ More consistant pedal feel under extended use, such as open-track or lots of very aggressive braking and any issues of fade are vastly reduced.

Glossary of terms:
ABS ~ Anti-Lock Braking system
Bleeding ~ Refers to replacing the fluid within your braking system
Brake dive ~ Refers to excessive compression of front suspension during braking
Brake fade ~ A general loss of effective braking due to one or more of several components and often heat related
Cross-drilled/slotted ~ methods to extract head and dust from wearing pads
DOT ~ Department Of Transportation who oversees safety issues of motorized vehicles on public roads
Heat soak ~ The point at which your brakes effectiveness is severely compromised (simple definition)
OEM ~ Original Equipment of Manufacturer

The first thing to understand: The brakes do not stop your car... the tires do! (< quote from TGR) No matter how impressive your brakes may be in slowing the wheels down, they will only work as well as your tires hold the road surface. This means that if you have tires that do not offer much friction, you will not stop in as short a distance as a tire better designed for the conditions. This actually leads well into yet MORE information one may need to consider, prior to upgrading existing brakes and is Choosing a new tire. If your wheels lock up or activate the ABS braking system, your stopping power will NOT be improved via this guide, but rather will come in other ways which I will address going forward.

Let's start with the most basic of information, for those that just don't know this stuff. What brakes do is turn kinetic energy into heat. That's it. (< another quote from TGR

) During this time, the rotors are being "squeazed" via the calipers and several items are getting placed under pressure based on how hard you push the pedal and the duration of this pressure. There is also a cumulative effect of heat during braking cycles, so why one should not "ride the brakes" while heading down a long hill. One should apply the brakes for a short time and then release them for a bit of cooling to the components.

The basic components consist of the following items:
Brake pads
rotors and/or drums
fluid within the braking system
Your foot

OEM Rotors: The SN95 OEM GT Mustang came equipped with solid-face/vented rotor (front) solid non-vented (rear) and are going to be fine for ALL legal street driving. As mentioned at the top of this thread, combined with SS lines, good pads and high-quality fluid, your car will have wonderful brakes for a very moderate cost.
13" Cobra rotors: There is some advantage to going with this larger rotor, when it comes to brake function. The first being a larger surface area in which to distribute/extract heat. The second being a mechanical advantage due an improvement of leverage from the caliper location relative to the rotor axis. The '99~'04 GT front rotors, are just under 11" diameter and the same year Cobra's are 13", so they look good, but will not be much advantage beyond this. One more thing to consider is clearance of your wheels and a 13" rotor. The Cobra uses a 17" wheel, but YOUR 17" wheels may not clear. You will need to do research to confirm fitment/clearance of your wheels in such a case.
Cross-drilled and/or slotted rotors: There are many aftermarket cross-drilled and/or slotted rotor designed as a direct fit with NO modifications necessary. This will be of some benefit to cooling, but to do this for anything but esthetics on a street-only ride is silly to me. These holes/slots can be a real problem if one gets them VERY hot, such as open-track or hard braking for an extended period of time. The street-designed rotors can warp and crack due to the weakness of the holes and cross-drilling. For this reason, many manufacturers only make cross-drilled OR slotted rotors and no longer both together. There are such rotors that will hold to the rigors of major heat and not crack, but are designed for race cars, so not applicable to those on the street or this thread.
Cross-drilled and/or slotted rotors and noise: You will get some added noise via the above rotors. A kind of a groan or humm is not unusual, but is more pronounced when braking hard. Lighter braking is generally not noticeable, so just keep this in mind when looking to purchase such a rotor.

OEM Calipers: The '94~'98 V6 & GT's came OEM with single piston both front and rear, while the '99~'04 V-6, GT and SN95 Cobra's came equipped with 2 piston front and single piston rear brake calipers. The piston or "pot" is essentially a small metal bucket that is between the fluid in the lines and the pads within the caliper. In such a case as the Mustangs we are discussing here, all of the pistons happen to be located on the inner-side of the rotors. When the brakes are applied, the fluid is "pushed" into the back-side of the piston and moves the pads toward each other to make ever increasing pressure on the rotors. The rotor is connected to the spinning wheels and the caliper is connected to the spindle up front and axle bracket out back. This clamping force slows the rotating wheel so you can stop for the kids at the cross-walk

4 piston calipers: The most common of caliper upgrades when looking to go beyond the OEM Cobra "swap". This caliper will squeaze evenly from both sides of the rotor, while the OEM ones will do so ONLY from one side. This means the "body" of the caliper must move freely to apply pressure from both pads into the rotor. Mechanically, this is not as reliable due to brake dust and wear issues that can effect the "balance" of movement. The 4-piston caliper will also be stronger and offer less flex under the pressure applied by the braking process. If there is flex of the caliper, this will translate into a "spongy" feel of brakes and creates inconsistancy in braking feel. This is one of the reasons why they are larger than the OEM ones found on your ride.
6~8 piston calipers: In my opinion, there is just no point to going beyond a 4 piston caliper on a street car and not sure I could justify it on a track car either. The reality is, if your braking system is good enough to lock your wheels or trigger the ABS system, you need only the proper fluid, good pads and SS lines to sustain it for stopping. There is an advantage to such a large brake pad, as you have an increased area in which to absorb/dissipate heat, but I see this as nearly a 100% marketing technique for gear-heads. For I could have a 12 piston caliper, 18" rotor and once my tires break their grip of the road, I am no longer in very much control of the stopping process... am I

4-piston calipers with cross-drilled and cross-drilled/slotted rotors:

SS lines: This refers to a short section (approx. 1' long) of flexable hose that connects the solid aluminum or SS main lines to each of the 4 calipers. The Mustang OEM lines are a very strong rubber, but rubber none-the-less. This rubber is placed under pressure during braking and can expand under its force. For this reason, the brakes can get a "spongy" feel, due to expansion, and create inconsistancies in braking. Temperature will effect the amount of expansion you may get and will compound the amount of this expansion and lead to additional "spongy" feel.

OEM Rubber & aftermarket SS brake lines:

Brake fluid: The brake fluid is what carries pressure from the brake pedal through the lines and applies pressure to the calipers to squeaze the rotors. Whenever anything is placed under physical "pressure", it will get hot and your braking system is no different. When the brakes are applied, based on how hard, the duration and the time elapsed between thier previous use, this heat can build up. When the heat builds above the boiling point of the fluid, it will begin to vaporize. While the fluid itself is NOT compressable, this vapor IS and where some of the brake fade issues come into play. The OEM fluid has a much lower boiling point than what is currently available and why it is on my list of upgrades for your braking system. There is no fluid that will NEVER reach such a point, but if you install a premium fluid, such as DOT5.1> or race quality, you should NEVER reach it. If you DO reach such a temp and your on the street... your doing something HORRIBLY wrong

Dry* boiling point of common fluids:
DOT3 ~ 401°
DOT4 ~ 446°
DOT5.1 ~ 518°
Wilwood High-Temp ~ 570°
Brembo LCF 600 ~ 601°
*wet boiling point is MUCH lower, as fluid absorbs moisture over time. For this, and other reasons, it should be replaced every 2 years to maintain consistant performance and less wear on internal parts of braking system. There is VERY little cost difference between these fluids and why I always say just get the good stuff

General information reguarding brake fluids:
... DOT5 is a silicon based fluid and not to be used in your Mustang. The seals were not designed for it and can fail over time.
... Brake fluids dry boiling point is more important then wet boiling point when used in a racing brake system.
... Passenger cars very rarely will undergo a brake fluid change making the wet boiling point more important.
... Using racing brake fluid will increase performance of the braking system.
... Never reuse fluid or mix types or brands of brake fluid.
... If fluid remains in container be sure to tightly seal and do not store for long periods of time.
... Purge system (complete drain) and replace fluid often.
... Immediately replace master cylinder reservoir cap following any maintenance.
... Some info is not applicable to open-track race cars, as different issues come into play.

Below list provided by "The ultimate brake fluid comparison chart":

Arranged by Dry boiling point:

DRY:401F -- WET:284F --- DOT3 MINIMUM (GLYCOL BASE)
DRY:446F -- WET:311F --- DOT4 MINIMUM (GLYCOL BASE)
DRY:500F -- WET:356F --- DOT5 MINIMUM (SILICONE BASE)
DRY:500F -- WET:356F --- DOT5.1 MINIMUM (GLYCOL BASE)
DRY:527F -- WET:302F --- AP RACING 551 ($12.95/0.5L OR 16.9 OZ)
DRY:527F -- WET:347F --- VALVOLINE SYNPOWER DOT3 & DOT4
DRY:536F -- WET:392F --- ATE SUPERBLUE/TYP200 ($9.95/1L)
DRY:543F -- WET:349F --- Endless The truth DOT 4 ($35/1L)
DRY:550F -- WET:284F --- PERFORMANCE Friction Z rated ($6.27/16 OZ)
DRY:550F -- WET:284F --- FORD HEAVY DUTY DOT 3 ($4/12 OZ)
DRY:570F -- WET:284F --- WILWOOD 570 ($5.65/12 OZ)
DRY:572F -- WET:284F --- US Brake/AFCO Racing 570 Gold
DRY:572F -- WET:421F --- US Brake/AFCO Racing Ultra HTX
DRY:577F -- WET:300F --- Brake Man
DRY:585F -- WET:421F --- Earl's Hypertemp 421
DRY:590F -- WET:410F --- AP RACING Super 600 ($16.95/0.5L OR 16.9 OZ)
DRY:593F -- WET:420F --- MOTUL RBF600 ($12.95/0.5L OR 16.9 OZ)
DRY:590F -- WET:518F --- CASTROL SRF ($69.00/1L 0R 33.8 OZ)
DRY:601F -- WET:399F --- BREMBO LCF 600 PLUS ($26.75/0.5L OR 16.9 OZ)
DRY:610F -- WET:421F --- NEO SYNTHETICS SUPER DOT 610($11.95/12 OZ)
DRY:610F -- WET:421F --- PROSPEED GS610 ($39.95/16 OZ)
DRY:617F -- WET:413F --- Endless RF-450 ($45/1L)
DRY:620F -- WET:425F --- COBALT SUPER XRF [seem to no longer be available]
DRY:622F -- WET:424F --- Endless RF-650
DRY:626F -- WET:417F --- WILWOOD EXP 600 ($16.95/0.5L 16.9 OZ)

Arranged by wet boiling point:

DRY:401F -- WET:284F --- DOT3 MINIMUM
DRY:550F -- WET:284F --- PERFORMANCE Friction Z rated
DRY:550F -- WET:284F --- FORD HEAVY DUTY DOT 3
DRY:570F -- WET:284F --- WILWOOD 570
DRY:572F -- WET:284F --- US Brake / AFCO Racing 570 Gold
DRY:577F -- WET:300F --- Brake Man
DRY:527F -- WET:302F --- AP RACING 551
DRY:446F -- WET:311F --- DOT4 MINIMUM
DRY:527F -- WET:347F --- VALVOLINE SYNPOWER DOT3 & DOT4
DRY:543F -- WET:349F --- Endless The truth DOT 4
DRY:500F -- WET:356F --- DOT5.1 MINIMUM (GLYCOL BASE)
DRY:536F -- WET:392F --- ATE SUPERBLUE/TYP200
DRY:601F -- WET:399F --- BREMBO LCF 600 PLUS
DRY:590F -- WET:410F --- AP RACING Super 600
DRY:617F -- WET:413F --- Endless RF-450
DRY:626F -- WET:417F --- WILWOOD EXP 600
DRY:572F -- WET:421F --- US Brake/AFCO Racing Ultra HTX
DRY:585F -- WET:421F --- Earl's Hypertemp 421
DRY:593F -- WET:420F --- MOTUL RBF600
DRY:610F -- WET:421F --- NEO SYNTHETICS SUPER DOT 610
DRY:610F -- WET:421F --- PROSPEED GS610
DRY:622F -- WET:424F --- Endless RF-650
DRY:620F -- WET:425F --- COBALT SUPER XRF [seem to no longer be available]
DRY:590F -- WET:518F --- CASTROL SRF

Brake pads: These are probably the single biggest variable in the system, in terms of how they respond to heat during braking. Some OEM pads will get heat-soaked soo fast, that the ability to stop can be nearly gone after only a few moments. It is very important to choose brake pads wisely to match the conditions in which one drives. Different manufacturers have different compounds that they ALL say are the best

Below is some examples of pads and will use Hawk Performance Street as an example:

... HPS ~ High Performance Street: Ferro-carbon compound low dust, low noise, not aggressive on rotors and very good friction on hot/cold rotors.

... PC ~ Performance Ceramic: very low dust, very quiet tend to work better when warmed through some braking
... HP Plus ~ AX and track compound: High friction when hot and resistant to fading

Brake pads:

So far we have addressed the brakes as a whole, but the fronts are going to realize the greatest benefit due to geometry and physics. That is not to say the rears brakes will not be improved, but we can do a little better than just pads and SS lines. Unfortunately, without significant suspension mods, not as much can be gained..... but certainly some, so read on, my friend

Cobra rear brake upgrade: As mentioned earlier, a larger rotor is beneficial due to improved leverage that is inhearent in the caliper being farther away from the axis of the rotor. It also retains a larger surface area in which to absorb/discipate heat. The rear Cobra rotor is not much larger than the OEM GT one, but has one more advantage over the OEM GT one... it is vented

Brake bias: Built into the braking system of all cars/trucks, is what is called a front/rear bias. A percentage of braking power is applied to the front in a different amount than the rear. This bias is due to a couple factors and mostly because of the weight and subsequent nose-dive of your car inhearant in the braking process. This is also due to geometry of the suspension system out back. This bias is pre-set via non-adjustable proportioning valve within the braking system. Theoretically, it may be adjustable, but DON'T mess with it. Messing the bias beyond what is approx. 70/30, can cause over-steer type issues created by skidding rear tires or ABS issues. As mentioned just above, some suspension mods can be done and this bias can be changed significantly to improve braking my a very noticable amount.

Proportioning valve: This is an adjustable control that completely replaces the OEM pre-set brake bias control found on your car. This can be installed on an otherwise OEM equipped car with or without a brake upgrade, but will likely deliver limited benefits. In such a case, at least some bias can be shifted from front to rear, but probably not a whole lot and may be hard to justify the expense/time involved to do so. This is NOT true, however, if one has done some rear suspension mods to address the geometery issues creating limiations in usefull adjustment of brake bias. The bias can be moved farther back, but depends on lots of factors and some specifics are discussed below.

Suspension mods to improve braking: Certain aftermarket "K" members can improve braking via relocation of the front wheels, as they are moved slighly from thier OEM location. The "A" arms sweep forward to create less brake-dive due to a change in suspension geometery. This leads to improved control under hard braking and less shifting of weight forward in such conditions. This will help maintain a better overall balance at such times and especially when turning. Another improvement, and even more significant, would be the addition of a torque-arm with pan-hard bar or watts-link rear suspension and removal of the UCA's. This so drastically changes the suspension geometry for the better, that the brake bias can be changed significantly for a MAJOR upgrade in the ability to stop ones car. To do this, is requires a lot of work to address the inhearent "end-play" of rear axles and aftermarket brakes pretty much exclusively found on race cars. If you are REALLY hardcore... this mod will cost you plenty, but be shifted back in time upon application of the brakes

.... some thoughts from the author:

Good braking technique: When I was first starting to drive, my father told me a few things about sitting behind the wheel. The first was to aways keep an eye WAY out and up front of me to keep up on changing conditions. Another, was to allow the brakes to cool between uses. To this day, I have never stomped on the brakes and held such pressure for more than a couple seconds (an exception or two!). If I STILL needed to slow down, I would repeat this process ONLY after having completely released them for as long a time as I could get a way with before needing them again. I have only one time, really felt the extent of extreme brake fade. This was about 10 years ago and was in my '85 GT heading down the highway on 100% OEM GT brakes. Long open stretch, no cars, no on-ramps and clear skies for several miles. Opened her up for a bit and got to about 120 MPH for a brief time before deciding to slow down. Well... I was not used to going soo fast, so I put the brakes on and did not slow down the amount I had anticipated, so, after letting them cool a bit, I applied them again. To my complete shock.... there was almost ZERO brakes left

The pedal just went WAY down, but was as if I was pushing in the clutch. What I hadn't realized is that the brakes had gotten VERY hot in only a few seconds, due to the very high speed in which I was moving. My instincts kicked in and placed MUCH less pressure on the pedal and allowed some additional cooling between braking to slow down and not have any issues beyond serious fear for a few moments. Of course, this took a MUCH greater distance in which to reduce my speed than I had originally anticipated. Now... had there been another car entering the road or something for which I HAD to stop faster, I would not have been able to and might not be here today and writing the post

My car today would NOT have such an issue in the identical circumstance, as I have brakes that will work WELL beyond what Ford had intended and just may save my life one day

Jazzer The Cat

*TGR = ReverendDexter

Last edited by Jazzer The Cat; 11-11-2011 at 09:18 PM.