Spring question. GT with IRS - Ford Mustang Forums : Corral.net Mustang Forum
 
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post #1 of 16 Old 01-16-2006, 10:33 AM Thread Starter
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Spring question. GT with IRS

I'm really confused on what to do here. I've got a 2004 Mustang GT (Novi blown) with a 2003 Cobra suspension in it (both front and rear). Right now with the Bilstein front and rear shocks/struts and the stock 03 Cobra coupe springs in the car, the front is trying to sit higher than the rear. I think the front fender is ~1/4" higher than the rear fender. Needless to say I don't like that look.....

So my question is, how do I get this car to sit level or with a slight rake to the front. On my old setup with the solid (H&R Race springs on stock shocks and struts) I could have withstood a firmer ride. The suspension was too complient for my liking. It felt like a Mustang SHOULD feel from the factory, which isn't what I want. All of the major roads down here in FL have been re-paved within the last 3 years so all are smooth. I'm not worried about how stiff the setup is going to be. I also cannot afford nor do I want to do coil-overs at the moment.

Before I went to IRS, I was going to swap out my H&R Race springs for the Super Race when I got new shocks/struts, but I see that H&R doesn't make a super race spring for the 03-04 Cobra. Could I put a super race from a GT on the front and a race for a Cobra on the rear? Will it sit level?

Here's some figures from MM:
99-04 GT HT
Race: Front 750-850(1.25") Rear 260-280(1.00")
Super Race: Front 950-1050(1.25") Rear 260-300(1.25")

99-04 Cobra HT (add an additional 3/8" lowering for 03-04 Cobra)
Race: Front 750-850(1.50-1.70") Rear 770(1.40-1.50")

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post #2 of 16 Old 01-16-2006, 11:32 AM
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I have a very similar setup. But I cut the 03 springs to lower the whole car. There is a considerable weight difference between the nose of a GT and the nose of an 03-04 Cobra. When I first installed the Cobra springs on the front of my GT, the ride height actually increased. I believe I cut 1.5 coils off. Ride is nice and firm. Sits perfectly.


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post #3 of 16 Old 01-16-2006, 08:06 PM Thread Starter
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Anybody else?
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post #4 of 16 Old 01-17-2006, 08:04 AM
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You're better off calling Maximum Motorsports to get the answer on that one. I don't think that many people here have done this swap. Looks like most of them have gotten rid of their IRS for a solid axle in modt cases. Just call them and get the advice from people who do it every day. Are you going to the Indian River autox with us next month? And I saw shawns rear seat delete kit he made, looks just like the one I bought, except it fits better. Is yours done?
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post #5 of 16 Old 01-17-2006, 08:06 AM
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Almost forgot, I read an article in Grassroots Motorsports recently about a guy with 99 cobra that has Griggs racing suspension on it. It gave some pretty good technical info on how the IRS and solid axle works and what can be done to fix the problem. I'll give you the article.
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post #6 of 16 Old 01-17-2006, 09:19 AM Thread Starter
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Quote:
Originally Posted by SCCARACERGT
Almost forgot, I read an article in Grassroots Motorsports recently about a guy with 99 cobra that has Griggs racing suspension on it. It gave some pretty good technical info on how the IRS and solid axle works and what can be done to fix the problem. I'll give you the article.
Awesome, thanks.

Yea I guess i'll just call MM sometime this week and see what they say. This has me completely stumped......

I haven't seen the finished product yet, but Shawn seems to be happy with it. Mine should be done Thursday.

I prolly won't race, but i'll come with. Those are the people who didn't let me have my 1st place trophy.
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post #7 of 16 Old 01-17-2006, 01:24 PM
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I think if you're the only one competing in your class, they don't give you a trophy. Because truthfully you had no competition anyway. Anyway, I decided to go with the spec stage 1 clutch. It's only $210 and it sais it can handle 450lb/ft of torque, which I obviously don't have right now. So it's better than stock and not as much as any other clutch out there for that piece of crap 3650. I'll let you know when i get it because we're going to be puting it in ourselves. There's no experience like hands on.
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post #8 of 16 Old 01-17-2006, 01:59 PM Thread Starter
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Yea well I still wanted my damn trophy haha. I only have a 2nd place .

I HATED my Spec, but yet I only had the 2, 3, and the 3.5. I never tried the stage 1. The Stage 2 wasn't TOO bad, but it doesn't compare with my McLeoud. It shouldn't be too hard to install. I had my stock 3650 off the car in ~45 mins. The starter bolts and something else was a ***** to do. I don't remember it exactly.

I want a stock 3650 oh so badly. My TKO is quite possibly the worst trans. i've ever driven on other than the T-56.
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post #9 of 16 Old 01-17-2006, 04:50 PM
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I just wanted something a little better than a stock replacement and all I could find was the spec clutch, for a reasonable price. I ordered it today from CFM and it should be here on Friday. So it'll be a fun weekend.
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post #10 of 16 Old 01-17-2006, 08:13 PM
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Guys, also contact Sean Hyland Motorsports, Modular Mustang Racing MMR, and ask more around the forums. MM and Griggs are good, but there are a few other solutions, and you will save some money. I am running IRS still.
Mostly, this question highly depends on your application - do you want to set it up for street, road racing, drag racing, auto-X ???

andy


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post #11 of 16 Old 01-17-2006, 11:15 PM Thread Starter
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Quote:
Originally Posted by v8cobra99
Guys, also contact Sean Hyland Motorsports, Modular Mustang Racing MMR, and ask more around the forums. MM and Griggs are good, but there are a few other solutions, and you will save some money. I am running IRS still.
Mostly, this question highly depends on your application - do you want to set it up for street, road racing, drag racing, auto-X ???

andy
The car is a everyday daily driver, but I do autox it and don't mind a firm ride. My H&R Race springs were too non-aggressive for my liking.

Last edited by SteedaGT; 01-18-2006 at 11:22 AM.
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post #12 of 16 Old 01-19-2006, 12:15 AM
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SteedaGT - I had thought MMR also offered rear-coil over kits for IRS setups, but they told me no in fact just today. Maximum Motorsports might be the best and only solution, I am not sure.... But for the $400 to $500 bucks, it is not a lot of money to spend anyway, so just go with MM...
For me, I am using Steeda 800lbs race springs standard type in the rear, non coil over. But I have full MM setup in the front with coil over and 475lbs springs.... but my application is full race....

andy

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post #13 of 16 Old 01-19-2006, 09:47 AM Thread Starter
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Quote:
Originally Posted by v8cobra99
SteedaGT - I had thought MMR also offered rear-coil over kits for IRS setups, but they told me no in fact just today. Maximum Motorsports might be the best and only solution, I am not sure.... But for the $400 to $500 bucks, it is not a lot of money to spend anyway, so just go with MM...
For me, I am using Steeda 800lbs race springs standard type in the rear, non coil over. But I have full MM setup in the front with coil over and 475lbs springs.... but my application is full race....

andy
Yea that sounds rather stiff.....

I'm thinking 400lbs up front, but i'm pretty undecieded on the rear. The rear springs I was wanting to use were 770's, so however that converts to coil-overs.
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post #14 of 16 Old 01-19-2006, 12:28 PM
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400lbs coil overs will still be pretty stiff, nearly double stiff from stock... There is a mathematical equation for the spring rates, I am sure someone around here has it.... my guess is a 400lbs coil over spring equates to a 700 to 800 lbs standard type.

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post #15 of 16 Old 01-19-2006, 01:04 PM
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Sean Hyland Motorsports does have rear coil over kits/shocks for IRS setups.
http://www.seanhylandmotorsport.com/...f6ee804c1a168d

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post #16 of 16 Old 01-19-2006, 01:49 PM Thread Starter
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Quote:
Originally Posted by v8cobra99
400lbs coil overs will still be pretty stiff, nearly double stiff from stock... There is a mathematical equation for the spring rates, I am sure someone around here has it.... my guess is a 400lbs coil over spring equates to a 700 to 800 lbs standard type.
I want to go stiffer than my H&R Race series springs that I had on the stick axle setup so w/e that would be.
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