IRS, who has swapped to it??
09-24-2008, 05:33 PM
#12
5th Gear Member
Join Date: Nov 2005
Location: MN
Posts: 4,412
Definitely a swap I'm looking to do. I may have the worlds heaviest SN-95 but I don't care, I think that would totally be worth the ride difference.
The purpose for my car is very similar to yours. I just want a car that makes driving as enjoyable as possible. I think BraMas is working on this swap too. So hopefully I can scope it out before I do it.
The purpose for my car is very similar to yours. I just want a car that makes driving as enjoyable as possible. I think BraMas is working on this swap too. So hopefully I can scope it out before I do it.
09-24-2008, 08:02 PM
#16
Mike there is a guy on our site that has done a few. He had alot of good info I will find he screen name and PM it to you.
There is a guy on SVT that sells a complete Derlin bushing kit.If you want the link I can post it on our site. not sure if MF will let me post it
FYI I flipped off my dust covered IRS as I walked by it tonight
There is a guy on SVT that sells a complete Derlin bushing kit.If you want the link I can post it on our site. not sure if MF will let me post it
FYI I flipped off my dust covered IRS as I walked by it tonight
Last edited by BraMas; 09-24-2008 at 08:05 PM.
09-24-2008, 08:08 PM
#17
2nd Gear Member
Join Date: Jun 2008
Location:
Posts: 256
Yo Mike you should've just asked me 
i've done it a couple times already.
SRA to IRS is very simple / straight forward swap. depending on what year it came from and how many miles will depend on how much wheel hop you'll have due to the fact that bushings could be either destroyed/beaten or brand new looking. I hope you didn't pay too much for that 04 IRS :x
Driveability is like tons smoother, i never realized how little the SRA did for dampening the road. I remembered your car is boosted right now so before even installing it or driving it hard with the IRS in, may i recommend getting a Billetflow IRS Cover Brace (something that all 03/04 Cobra owners figure they don't need then they blow their covers off & end up damaging the LSD / Ring&Pinion with possible housing). Cornering / Suspension wise, it's waaaay better compared to the SRA which i'd understeer like mad (which typically isn't what you want) and now i just slightly oversteer only when i give it too much gas. Typically IRS is wanted if you like to RR & SRA for Drag. I can take my friend's Track 350z in turns no problem pulling away.
--------------------------------
Wheel Hop Occurs because...
Differential case is mounted with soft bushings, allows it to rotate side to side and front to back, MM bushings cure this.
IRS Cradle is mounted with flexible bushings, allows it to move in relation to cars chassis mounting points, MM polyurethane bushings cure this.
Upper and lower countrol arms are mounted with flexible bushings, this allows the wheel to move forward/back when you only really want it to move up/down, MM delrin bushings, aluminum sleeves cure this.
Toe link bars are very small diameter and flexible, weakest point of support for the wheel, allows wheel to turn in/out and move forward/back, using PHP toe link bars cures this.
Rear IRS subframe mounts are cantilevered 3+" from the rear subframe, allows for up/down flex in the IRS cradle mounting point, using Billetflow IRS Mount brackets with backer plates cures this.
another thing you'll have to consider is that you have a vert, meaning the springs you have now are specific for verts (having low spring rates thus wheelhop). you'll want to replace those with some coupe specific springs or coilovers.
-----------------------------------
If you plan on keeping your car under 500rwhp, you wont have to worry about lvl 5 halfshafts, Toe Link Bars, Diff Cooler(still recommended) or U/L Control Arm Bushings and only worry about this list im giving you.
(From 1-7 Being 1 as the most necessary)
1)Billetflow Diff Cover Brace $160
Numerous stock Cobras have grenaded the flimsy diff cover. The damage only gets worse as you mod these cars. Get a Billetflow Diff brace ASAP on any IRS Cobra and you will thank me later. They are guaranteed to never break or full refund. This is not a bullsh*t advertisement, this is a critical reinforcing mod to keep your diff/driveshaft/trans safe from breakage. http://www.billetflow.com/irs_brace.htm
2)MM Diff bushings $50 or $250
like the ones offered by Maximum Motorsports. They sell a Urethane kit for $50 and a fancy adjustable Aluminum set for $250. There have been other companies that offer low quality urethane bushings that melt and deform in this location (diff gets pretty warm) but I have not seen a report of these MM Urethane ones yet. They may be able to take the heat, I cannot say for sure so no endorsement for their urethane ones yet. Their aluminum ones will work fine. Also any other source for aluminum bushings for here could be used as well. One last thing to consider is the noise of the diff (gear whine) will be transferred more and be audible in the interior depending on how loud your car is. I use aluminum here and have a loud exhaust and can still hear the gears. The front two are the ones susceptible to heat, the rear bushings can be delrin, UMHW, nylatron, urethane..... just reuse the aluminum sleeve from the stock bushing or something like it and it will work fine. http://www.maximummotorsports.com/in...Path=21_88_194
3)MMFLSFC's installed $250-300 installed
Have them properly welded in by an experienced installer on a drive on lift. The drive on lift is absolutely critical, if the weight is not on the wheels you are unknowingly permanently warping and binding your chassis. Other brands like Global West, Laurel Mountain Mustangs and UMI Performance have shown good results. I currently have HANS Force subframes and do not like them, way too much flex, pass on them.
4)MM IRS Bushings $50 with 14mm bolts/nuts $15
from Maximum Motorsports. Others sell them but I have used three sets of these now (3 different cars) with excellent results. Be CERTAIN to order the 14mm bolts and nuts when you buy your bushings. MM Sells only the OEM strength ones so no need to worry. http://www.maximummotorsports.com/in...Path=21_88_192
5)Billetflow IRS Mount Brackets $50
3-hole design with backing plates, available now from Billetflow. Sometimes called Mathis Brackets these are an important part of the system. The outer portion of the rear IRS mount bracket is cantilevered out away from any support and free to flex under load. William Mathis originally developed them. I was making a set of my own and cut out a simple cardboard template. While marking the holes to drill I tapped through the template using a hammer and phillips screwdriver. A very mild tap resulted in me piercing the inner wheelhouse metal. Further research showed this metal to be less than 1mm thick and very weak. I did not trust such thin metal to withstand the stress so I then developed a backing plate to make it a robust modification. http://www.billetflow.com/IRS_Brackets.htm
6)Used coupe springs $50 (Est) (only for verts)
or heavier (especially in verts). Coupe rear springs are 600 lb/in, verts are 470lb/in. 650lb/in Cobra R springs have been reported as giving excellent results. I experimented with cutting stock springs and found 1/2 coil cut circumferentially will approximate most commonly available lowering springs. Drop will be 1"-1.25" with 1/2 coil cut. 1/2 coil = one "C" shape.
7)Nitto DR $375-$425 installed (Cheap) or Alternative better DR
M/T DR or BFG DR. Nitto DR are an intermediate traction DR, no where near the traction from an M/T or BFG. Nittos will last 3-4x longer and not kill you in rain though. M/T and BFG are dry only tires, you will not be able to drive your car at all in rain/snow with either. Just know how dangerous DR can be in wet conditions, extreme caution is what I urge before depending on DR an a daily driver, very bad idea. One of the benefits of the mods above this point is it reduces the need for sticky tires to fight hop. You can skip tires if you have done all the above mods, the only negative is you will have more wheel spin.
-------------------------------
but basically... IRS is well worth it if you're into Road Racing and love a comfortable Ride plus having an exhaust wrap around your tank is just sexy.
i've done it a couple times already.SRA to IRS is very simple / straight forward swap. depending on what year it came from and how many miles will depend on how much wheel hop you'll have due to the fact that bushings could be either destroyed/beaten or brand new looking. I hope you didn't pay too much for that 04 IRS :x
Driveability is like tons smoother, i never realized how little the SRA did for dampening the road. I remembered your car is boosted right now so before even installing it or driving it hard with the IRS in, may i recommend getting a Billetflow IRS Cover Brace (something that all 03/04 Cobra owners figure they don't need then they blow their covers off & end up damaging the LSD / Ring&Pinion with possible housing). Cornering / Suspension wise, it's waaaay better compared to the SRA which i'd understeer like mad (which typically isn't what you want) and now i just slightly oversteer only when i give it too much gas. Typically IRS is wanted if you like to RR & SRA for Drag. I can take my friend's Track 350z in turns no problem pulling away.
--------------------------------
Wheel Hop Occurs because...
Differential case is mounted with soft bushings, allows it to rotate side to side and front to back, MM bushings cure this.
IRS Cradle is mounted with flexible bushings, allows it to move in relation to cars chassis mounting points, MM polyurethane bushings cure this.
Upper and lower countrol arms are mounted with flexible bushings, this allows the wheel to move forward/back when you only really want it to move up/down, MM delrin bushings, aluminum sleeves cure this.
Toe link bars are very small diameter and flexible, weakest point of support for the wheel, allows wheel to turn in/out and move forward/back, using PHP toe link bars cures this.
Rear IRS subframe mounts are cantilevered 3+" from the rear subframe, allows for up/down flex in the IRS cradle mounting point, using Billetflow IRS Mount brackets with backer plates cures this.
another thing you'll have to consider is that you have a vert, meaning the springs you have now are specific for verts (having low spring rates thus wheelhop). you'll want to replace those with some coupe specific springs or coilovers.
-----------------------------------
If you plan on keeping your car under 500rwhp, you wont have to worry about lvl 5 halfshafts, Toe Link Bars, Diff Cooler(still recommended) or U/L Control Arm Bushings and only worry about this list im giving you.
(From 1-7 Being 1 as the most necessary)
1)Billetflow Diff Cover Brace $160
Numerous stock Cobras have grenaded the flimsy diff cover. The damage only gets worse as you mod these cars. Get a Billetflow Diff brace ASAP on any IRS Cobra and you will thank me later. They are guaranteed to never break or full refund. This is not a bullsh*t advertisement, this is a critical reinforcing mod to keep your diff/driveshaft/trans safe from breakage. http://www.billetflow.com/irs_brace.htm
2)MM Diff bushings $50 or $250
like the ones offered by Maximum Motorsports. They sell a Urethane kit for $50 and a fancy adjustable Aluminum set for $250. There have been other companies that offer low quality urethane bushings that melt and deform in this location (diff gets pretty warm) but I have not seen a report of these MM Urethane ones yet. They may be able to take the heat, I cannot say for sure so no endorsement for their urethane ones yet. Their aluminum ones will work fine. Also any other source for aluminum bushings for here could be used as well. One last thing to consider is the noise of the diff (gear whine) will be transferred more and be audible in the interior depending on how loud your car is. I use aluminum here and have a loud exhaust and can still hear the gears. The front two are the ones susceptible to heat, the rear bushings can be delrin, UMHW, nylatron, urethane..... just reuse the aluminum sleeve from the stock bushing or something like it and it will work fine. http://www.maximummotorsports.com/in...Path=21_88_194
3)MMFLSFC's installed $250-300 installed
Have them properly welded in by an experienced installer on a drive on lift. The drive on lift is absolutely critical, if the weight is not on the wheels you are unknowingly permanently warping and binding your chassis. Other brands like Global West, Laurel Mountain Mustangs and UMI Performance have shown good results. I currently have HANS Force subframes and do not like them, way too much flex, pass on them.
4)MM IRS Bushings $50 with 14mm bolts/nuts $15
from Maximum Motorsports. Others sell them but I have used three sets of these now (3 different cars) with excellent results. Be CERTAIN to order the 14mm bolts and nuts when you buy your bushings. MM Sells only the OEM strength ones so no need to worry. http://www.maximummotorsports.com/in...Path=21_88_192
5)Billetflow IRS Mount Brackets $50
3-hole design with backing plates, available now from Billetflow. Sometimes called Mathis Brackets these are an important part of the system. The outer portion of the rear IRS mount bracket is cantilevered out away from any support and free to flex under load. William Mathis originally developed them. I was making a set of my own and cut out a simple cardboard template. While marking the holes to drill I tapped through the template using a hammer and phillips screwdriver. A very mild tap resulted in me piercing the inner wheelhouse metal. Further research showed this metal to be less than 1mm thick and very weak. I did not trust such thin metal to withstand the stress so I then developed a backing plate to make it a robust modification. http://www.billetflow.com/IRS_Brackets.htm
6)Used coupe springs $50 (Est) (only for verts)
or heavier (especially in verts). Coupe rear springs are 600 lb/in, verts are 470lb/in. 650lb/in Cobra R springs have been reported as giving excellent results. I experimented with cutting stock springs and found 1/2 coil cut circumferentially will approximate most commonly available lowering springs. Drop will be 1"-1.25" with 1/2 coil cut. 1/2 coil = one "C" shape.
7)Nitto DR $375-$425 installed (Cheap) or Alternative better DR
M/T DR or BFG DR. Nitto DR are an intermediate traction DR, no where near the traction from an M/T or BFG. Nittos will last 3-4x longer and not kill you in rain though. M/T and BFG are dry only tires, you will not be able to drive your car at all in rain/snow with either. Just know how dangerous DR can be in wet conditions, extreme caution is what I urge before depending on DR an a daily driver, very bad idea. One of the benefits of the mods above this point is it reduces the need for sticky tires to fight hop. You can skip tires if you have done all the above mods, the only negative is you will have more wheel spin.
-------------------------------
but basically... IRS is well worth it if you're into Road Racing and love a comfortable Ride
plus having an exhaust wrap around your tank is just sexy.
09-24-2008, 08:14 PM
#18
2nd Gear Member
Join Date: Jun 2008
Location:
Posts: 256
also yeah i forgot to mention that it does help with weight distribution being that the stock 96 GT Vert has a 57% Front / 43% Rear putting it closer to a 50/50 since the IRS weighs an extra 85lbs roughly depending on what model IRS you got (99/00R/01/03/04)
if you need instructions or pictures on how to do it, i also can provide one for you. for differential bushings, i wouldn't go half *** on those and get the aluminum ones cause my friend has the urethane ones and they didn't last as long as they should since that general area gets really hot. plus the new differential mount is way sturdier & ez to install. $250 for alum. bushings that'll last forever or $65 for ones that you'll have to replace eventually, you're call. also have torque specs for everything incase you're worried about it coming lose etc..
if you need instructions or pictures on how to do it, i also can provide one for you. for differential bushings, i wouldn't go half *** on those and get the aluminum ones cause my friend has the urethane ones and they didn't last as long as they should since that general area gets really hot. plus the new differential mount is way sturdier & ez to install. $250 for alum. bushings that'll last forever or $65 for ones that you'll have to replace eventually, you're call. also have torque specs for everything incase you're worried about it coming lose etc..
09-24-2008, 08:41 PM
#19
6th Gear Member
Thread Starter
Join Date: Feb 2006
Location: Virginia
Posts: 11,786
Mike there is a guy on our site that has done a few. He had alot of good info I will find he screen name and PM it to you.
There is a guy on SVT that sells a complete Derlin bushing kit.If you want the link I can post it on our site. not sure if MF will let me post it
FYI I flipped off my dust covered IRS as I walked by it tonight
There is a guy on SVT that sells a complete Derlin bushing kit.If you want the link I can post it on our site. not sure if MF will let me post it
FYI I flipped off my dust covered IRS as I walked by it tonight
I can't wait to install it. I just wanted to check out what everyone here has to say about it. I've read well over 100 threads about IRS over on SVTperf. I actually have a Bookmark Folder dedicated to SVT Perf on tech and Opinions. The technical of it is easy and I'm not worried about it. I'm mostly just having the jitters about switching to something SO MAJOR. I Never want to give up comfort with my car since that is more of an importance than even high Hp.
09-24-2008, 08:53 PM
#20
2nd Gear Member
Join Date: Jun 2008
Location:
Posts: 256
yeah the comfort of the ride is tons better. IRS dampens the road soo well its amazing. feels like a real sports car. If i was in your position again (i was when i had the IRS) i'd pull the trigger and swap it in
its truely amazing.
its truely amazing.