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Discussion Starter #1
Has anyone done the IRS swap into a 94-95? If so what lowering springs did you use?
 

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I'm in the process of doing both my '95s. Both are getting MM coil overs, 550 lbs./in track car, 500 lbs./in. daily driver.

Jay
 

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Hoping to do my 94 next year. I would ask the guys at Maximum. I’ve spoken to them about doing the swap and their tech guys seem to know a fair amount about it. There are some bushings you should swap while the irs is out of the car.
 

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Discussion Starter #4
Well the swap is already done and the car tracks perfectly. I did replace all bushings with full tilt boogie racing bushings I'm just not liking the stance. Not sure if the cobra springs are to tall or just to stout for a 94.
 

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Overrated probably? I imagine one could accomplish the same with shocks/struts, springs, and a decent rear control arm setup. If you want to handle even better get a panhard bar. The solid axle will be better for off the line grip, and with aftermarket parts it’ll handle well as well. I don’t race a road course or auto cross, but I’ve never felt that it was lacking in the handling department going around corners on public roads in a brisk manner. If I give it too much gas (either from a stand still or cornering) the rear end will come around. But I bet a panhard bar will help that. It didn’t come around so easy prior to the supercharger, and the j&m rear control arms tamed it a lot.
IRS- What for?
 

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Overrated probably? I imagine one could accomplish the same with shocks/struts, springs, and a decent rear control arm setup. If you want to handle even better get a panhard bar. The solid axle will be better for off the line grip, and with aftermarket parts it’ll handle well as well. I don’t race a road course or auto cross, but I’ve never felt that it was lacking in the handling department going around corners on public roads in a brisk manner. If I give it too much gas (either from a stand still or cornering) the rear end will come around. But I bet a panhard bar will help that. It didn’t come around so easy prior to the supercharger, and the j&m rear control arms tamed it a lot.
IRS- What for?
A lot of people are misinformed about the SN95 chassis.

The 1994-1998 Saleen S351 mustangs were tested as handling better than the comparable year Porsche 911 as the Saleens were equipped with conventional stock style lowering springs, racecraft shocks, and stock 4 link with a panhard bar. The Saleen S351's were very successful on the track, and beat a good number of Porsche 911's.

The stock 1995 Cobra R Mustang with conventional eibach lowering springs, and Koni Yellow shocks with stock 4 link, no panhard bar pulled a .96 g during road tests on stock tires. That's almost just as good as a 2018 S550 GT mustang that pulls .98 g on the skid pad. The 1995 Cobra R is lighter than the S550, and the 1995 Saleen S351 is even lighter than the Cobra R.

I'm certain my 1995 GT pulls more than 1 g in the corners. My car has Eibach prokit springs, Tokico blues, MM rear lower control arms, MM subframe connectors, Upper/Lower MM front Chassis braces, and Polyurethane swaybar bushings/end links... I'm also pretty sure my T1 wing pushes the ass end down quite a bit. My Nitto 555 G2 tires also made a huge difference. The rear of my car does not break loose in corners, or get sideways like it did when it was on stock suspension. Modern tires do wonders for these cars. My car also puts down 357 lbs of torque to the rear wheels.

With that said the IRS is a great swap for people who want a less bumpy ride, or a better handling ride at the limit, but only if you upgrade the bushings. I'd think that if you were tracking the car an IRS with upgraded bushings would be Ideal. However I know the solid axle Griggs GR40 96 Cobra is quite possibly one of the best handling cars in the world. So I don't know, it's all up to preference.
 

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A lot of people are misinformed about the SN95 chassis.

The 1994-1998 Saleen S351 mustangs were tested as handling better than the comparable year Porsche 911 as the Saleens were equipped with conventional stock style lowering springs, racecraft shocks, and stock 4 link with a panhard bar. The Saleen S351's were very successful on the track, and beat a good number of Porsche 911's.

The stock 1995 Cobra R Mustang with conventional eibach lowering springs, and Koni Yellow shocks with stock 4 link, no panhard bar pulled a .96 g during road tests on stock tires. That's almost just as good as a 2018 S550 GT mustang that pulls .98 g on the skid pad. The 1995 Cobra R is lighter than the S550, and the 1995 Saleen S351 is even lighter than the Cobra R.

I'm certain my 1995 GT pulls more than 1 g in the corners. My car has Eibach prokit springs, Tokico blues, MM rear lower control arms, MM subframe connectors, Upper/Lower MM front Chassis braces, and Polyurethane swaybar bushings/end links... I'm also pretty sure my T1 wing pushes the ass end down quite a bit. My Nitto 555 G2 tires also made a huge difference. The rear of my car does not break loose in corners, or get sideways like it did when it was on stock suspension. Modern tires do wonders for these cars. My car also puts down 357 lbs of torque to the rear wheels.

With that said the IRS is a great swap for people who want a less bumpy ride, or a better handling ride at the limit, but only if you upgrade the bushings. I'd think that if you were tracking the car an IRS with upgraded bushings would be Ideal. However I know the solid axle Griggs GR40 96 Cobra is quite possibly one of the best handling cars in the world. So I don't know, it's all up to preference.
Preference and marketing I think.
 

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However I know the solid axle Griggs GR40 96 Cobra is quite possibly one of the best handling cars in the world. So I don't know, it's all up to preference.
It also has a SLA front suspension, which is a game changer VS the standard MacPherson strut setup.
 

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Discussion Starter #11
Didn't think I would have all this response but is much appreciated. My car with the sra in it would slide across the track even with coil overs and a panard bar setup. But with the IRS the car reacts to changes on the track that the sra couldn't such as out of a turn up hill and hairpin turns amongst others. The wheel hop is non existent also. I did do full tilt boogie racing bushings on it which I believe has made a difference also along with adjustable rear shocks. Just like everything else it has pros and cons I know but actually had to see if it could be done. Thanks again for those responses keep them coming if you like.
 

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It also has a SLA front suspension, which is a game changer VS the standard MacPherson strut setup.
Speaking of SLA, that is exactly what a Cobra IRS is. Camber, toe, and bumpsteer are all adjustable. When set up to their max capabilities, the IRS will easily out handle the live axle, straight line acceleration being the only advantage a torque arm/panhard equipped live axle has over the IRS. Initial camber settings, plus camber gain during compression, for instance are major advantages over the 0* live axle, which goes into positive camber on the outside tire while turning. The ability of an IRS to walk one side of the rear over a berm at the apex of a corner without upsetting the entire rear suspension is also a major advantage.

Jack from MM recently commented about the stiffness of the Cobra IRS anti-sway bars and suggested using a 35mm Eibach front bar as a decent match to avoid oversteer, which can be a dangerous condition.

Jay
 

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IRS makes a huge difference, I don't think I'll ever own another SN95 chassis without one unless its setup for straight line speed only. Stock they have a ton of issues, after the Full Tilt treatment with a good set of shocks/springs or coilovers out back its a completely different animal.

Overrated probably? I imagine one could accomplish the same with shocks/struts, springs, and a decent rear control arm setup. If you want to handle even better get a panhard bar. The solid axle will be better for off the line grip, and with aftermarket parts it’ll handle well as well. I don’t race a road course or auto cross, but I’ve never felt that it was lacking in the handling department going around corners on public roads in a brisk manner. If I give it too much gas (either from a stand still or cornering) the rear end will come around. But I bet a panhard bar will help that. It didn’t come around so easy prior to the supercharger, and the j&m rear control arms tamed it a lot.
IRS- What for?
That's a lot of words to say you've never driven a properly setup IRS or 3 link and any input is pure speculation. Wrong speculation I might add.

Didn't think I would have all this response but is much appreciated. My car with the sra in it would slide across the track even with coil overs and a panard bar setup. But with the IRS the car reacts to changes on the track that the sra couldn't such as out of a turn up hill and hairpin turns amongst others. The wheel hop is non existent also. I did do full tilt boogie racing bushings on it which I believe has made a difference also along with adjustable rear shocks. Just like everything else it has pros and cons I know but actually had to see if it could be done. Thanks again for those responses keep them coming if you like.
FTBR definitely fixes all the issues. I did everything except I put Prothane in the subframe. Delrin in the LCAs, UCAs, solid/delrin diff mount bushings and the Full Tilt tie rods. Also new cross axis links, Eibach swaybar and adjustable endlinks.

Speaking of SLA, that is exactly what a Cobra IRS is. Camber, toe, and bumpsteer are all adjustable. When set up to their max capabilities, the IRS will easily out handle the live axle, straight line acceleration being the only advantage a torque arm/panhard equipped live axle has over the IRS. Initial camber settings, plus camber gain during compression, for instance are major advantages over the 0* live axle, which goes into positive camber on the outside tire while turning. The ability of an IRS to walk one side of the rear over a berm at the apex of a corner without upsetting the entire rear suspension is also a major advantage.

Jack from MM recently commented about the stiffness of the Cobra IRS anti-sway bars and suggested using a 35mm Eibach front bar as a decent match to avoid oversteer, which can be a dangerous condition.

Jay
Yep, the Cobra IRS is a full blown SLA out back. I don't have coilovers on mine out back, just D specs with Steeda springs and its fine honestly. I may go coilovers in the future if I swap out the D Specs for Konis. Good to hear about the front swaybar too, I have a 35mm Steeda unit in place already up front.
 

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IRS makes a huge difference, I don't think I'll ever own another SN95 chassis without one unless its setup for straight line speed only. Stock they have a ton of issues, after the Full Tilt treatment with a good set of shocks/springs or coilovers out back its a completely different animal.



That's a lot of words to say you've never driven a properly setup IRS or 3 link and any input is pure speculation. Wrong speculation I might add.



FTBR definitely fixes all the issues. I did everything except I put Prothane in the subframe. Delrin in the LCAs, UCAs, solid/delrin diff mount bushings and the Full Tilt tie rods. Also new cross axis links, Eibach swaybar and adjustable endlinks.



Yep, the Cobra IRS is a full blown SLA out back. I don't have coilovers on mine out back, just D specs with Steeda springs and its fine honestly. I may go coilovers in the future if I swap out the D Specs for Konis. Good to hear about the front swaybar too, I have a 35mm Steeda unit in place already up front.
Is yours a road course racer?
Here’s a decent comparison I think of a solid axle vs IRS on a race track. Both street cars. The ‘03 Camaro vs the ‘03 Cobra.
“What surprised us was how close their lap times were, despite the mechanical differences. The lap times were nearly identical and Smith circuited the track repeatedly, showing no mercy. Ultimately, the Mustang had the fastest time of the day, a 1:26.25 around the 1.35-mile course, with the SS clocking in at 1:26.57. The fact that the Bowtie was giving up 60 rear wheel horsepower means three-tenths is nothing.”

 

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That's not actually a very good comparison at all. The Terminator is super nose heavy like driving a boat, plus there was no 03 Camaro... 02? Terminator is meant to go in a straight line, not handle, at all. The 99-04 IRS factory is also mediocre at best because of all the rubber in it. Replace it all with Delrin and better parts and it wakes up. That''s why I said PROPERLY SET UP IRS or stick axle 3 link... not a factory setup.

Yes my car is being set up to handle and we have one of the bigger tracks in Europe 20 minutes away.
 

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That's not actually a very good comparison at all. The Terminator is super nose heavy like driving a boat, plus there was no 03 Camaro... 02? Terminator is meant to go in a straight line, not handle, at all. The 99-04 IRS factory is also mediocre at best because of all the rubber in it. Replace it all with Delrin and better parts and it wakes up. That''s why I said PROPERLY SET UP IRS or stick axle 3 link... not a factory setup.

Yes my car is being set up to handle and we have one of the bigger tracks in Europe 20 minutes away.
I wouldn't say the 03-04 Cobra was mean't for straight line only. It did beat the Camaro in handling. The stock IRS is mean't for street use, and needed to be soft for the masses of people buying it who would just be driving around town, and not a track.

With that said I would by no means be afraid of a 4th Gen F-body as the 1995 Cobra R, and 96 SVT Cobra beat those several times in IMSA factory stock competitions... well the 1995 Cobra R also beat the Mark 4 Supra, BMW's, and 4th Gen F-body's with the unpredictable factory 4 link that supposedly likes to slide off the track all the time.

Of course the modified IRS is absolutely better than the solid axle. However, I think people tend to over hype certain cars that actually got their asses handed to them by the 95 Cobra R.
 

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That's not actually a very good comparison at all. The Terminator is super nose heavy like driving a boat, plus there was no 03 Camaro... 02? Terminator is meant to go in a straight line, not handle, at all. The 99-04 IRS factory is also mediocre at best because of all the rubber in it. Replace it all with Delrin and better parts and it wakes up. That''s why I said PROPERLY SET UP IRS or stick axle 3 link... not a factory setup.

Yes my car is being set up to handle and we have one of the bigger tracks in Europe 20 minutes away.
Ford went with an IRS because IRS is better for drag racing!? So... Why didn’t you stick with the solid rear for your European tracks?
The stock rear suspension “sucks” on the solid axle mustangs as far as handling aspects go, and you say that the Cobra’s IRS stinks too. However, both can be modified to handle well, or “well enough.” Heck the F-Body kept up with the cobra with it’s factory suspension. Nose heavy or not the Cobra was still putting down more power. You’d think the extra power would make up time in the straights, but I guess not.
I tried to find an apples to apples comparison where someone went from the stock SN95 suspension to independent, and either a skidpad or a slalom course. The closest I could come up with was a review of the ‘99 Cobra. Car and Driver stated that the IRS Cobra was better on the skidpad by .03g’s. Is .03g’s a big difference? They also said that the Cobra had 245/45ZR-17 BFGoodrich Comp T/A’s. If those tires are better than whatever they tested the GT had then the test results might be slightly skewed.
I just found this article on the ‘03 Mach 1. So pseudo apples to apples with stock parts, “The Mach I cleared our 600-foot slalom at 63.6 mph, just a tick slower than the IRS-equipped Cobra (64.3) and solid-axle Bullitt (66.0). Ford engineers explained why the Mach 1 was slower through the cones.” So stock for stock with stock parts the IRS didn’t help all that much. Can we agree on that?
I guess what we need is someone with a road race ready solid axle vs a road race ready IRS setup on the same car or type of car, so we can see how much faster the IRS is. Because both can be modified to be better than the factory “rubber” suspension. You saying that you’re race ready IRS can out handle Joe Blow’s stock solid axle suspension isn’t that good of a comparison is it? Neither is saying something like, $100k car with irs can out handle this $20k solid axle car any day... In the end it’s all going to come down to who spent the most money. But stock for stock it doesn’t sound like the IRS is a clear winner at anything.
Do you have any before and after lap times where the only difference was the rear suspension?

 

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Because my car is a street car first and foremost where the stick axle cannot compete with an IRS. Again, that's a lot of words for you've never driven a well setup 3 link or IRS. Or any car at a road course for that matter... Post all the articles from magazines you want, doesn't sub for actual IRL experience. You can have a car with a LOT less power run way faster times. Go drive a prepped Miata, you'll never have as much fun with 160hp as you will in one of those.

I've driven both, the IRS is better FOR THE STREET if you care about handling and its not close. If you are track prep only then the GR40 Griggs Cobra and some of the S197 stuff with the stick axle can be world class but even then its a toss up. For drag no idea why Ford went with the IRS for the Terminator, they shouldn't have but probably because they had it in all the New Edge Cobras prior. It does ok at the drag strip with the full tilt treatment and proper drag springs and shocks and drag setup up front but most ppl serious about drag do the SRA swap.

And at this point where the youngest New Edges are 16+ years old it doesn't matter what you had, the stock suspension needs replaced regardless.
 

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I wouldn't say the 03-04 Cobra was mean't for straight line only. It did beat the Camaro in handling. The stock IRS is mean't for street use, and needed to be soft for the masses of people buying it who would just be driving around town, and not a track.

With that said I would by no means be afraid of a 4th Gen F-body as the 1995 Cobra R, and 96 SVT Cobra beat those several times in IMSA factory stock competitions... well the 1995 Cobra R also beat the Mark 4 Supra, BMW's, and 4th Gen F-body's with the unpredictable factory 4 link that supposedly likes to slide off the track all the time.

Of course the modified IRS is absolutely better than the solid axle. However, I think people tend to over hype certain cars that actually got their asses handed to them by the 95 Cobra R.
A good driver can make up for a lot and in 1995 none of those cars really handled all that well... The 4 link does wander around and is downright dangerous going around corners when ppl start messing with the stock uppers. 3 link it or swap it or go with an IRS. I still catch myself easing up in corners my car is WELL within its capabilities to handle because I've had so many Foxes/SN95s with the 4 link. You wait for the rear to get squirrely like it always does but it never happens with the car I have now.

Also agreed about overhyped cars. The Supra being the king of overhype. Dyno queens most of the time, parts are expensive and most of the ones I've seen have ridiculous trap speeds but not great 1/4 times. Whatevs...
 

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A good driver can make up for a lot and in 1995 none of those cars really handled all that well... The 4 link does wander around and is downright dangerous going around corners when ppl start messing with the stock uppers. 3 link it or swap it or go with an IRS. I still catch myself easing up in corners my car is WELL within its capabilities to handle because I've had so many Foxes/SN95s with the 4 link. You wait for the rear to get squirrely like it always does but it never happens with the car I have now.

Also agreed about overhyped cars. The Supra being the king of overhype. Dyno queens most of the time, parts are expensive and most of the ones I've seen have ridiculous trap speeds but not great 1/4 times. Whatevs...
Did you ever put spherical bushings in all of your rear end bushings on the stock 4 link?
 
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