Coil overs on IRS? Need help hooking with 800+ whp

MalcolmV8

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Hey Guys,

So looking for options to make my IRS hook. I think a big part of the problem is the lack of weight transfer when I step on it.

My setup
IRS:
Factory shocks
MM urethane bushings throughout.
Stock coils cut down 1/2" turn or so
MM drag links
295/55/15 MT on 10x15 rims

Front:
UPR coil overs approximately stock stiffness on factory shocks.
Sway bar still in place.

The problem: A brand new set of tires will hook in 2nd gear if heated but they only hold for a few WOT pulls and just get shredded and tore up so quickly. I mean like a few pulls in one afternoon and they're done. Then the whole rest of the tires life it's worthless. I can punch it at 70+ mph and just tear them up laying black lines.

The instant torque and throttle response of the high compression motor and the TVS spinning hard is fun as hell but making it hook has been a challenge.

When I compare my car to other cars that hook a big thing I notice is how flat and stiff my car is on launch and acceleration where as you can see the other cars squat in the rear and the front come up. My car doesn't flex back and transfer weight and over stresses the hell out of the tires.

So my thoughts are some coil overs in the rear with soft coils to let the rear squat when I punch it.

I was looking at these Koni adjustable shocks
http://www.maximummotorsports.com/Koni-Single-Adjustable-Shock-modified-1999-04-Cobra-IRS-P1265.aspx

Which go with this matching MM coil over kit for the IRS and your choice of spring rate
http://www.maximummotorsports.com/C...-SA-Shocks-rear-1999-04-Mustang-IRS-P512.aspx

Has anybody used this? Any feed back? I hate to get all that and it makes no difference.

Up front I'm thinking of removing the sway bar and changing out those shocks/coil overs with something better. By better I mean an adjustable shock made for drag racing that will flex out easy on the hit and a softer spring that will let the front come up some. Thoughts?

Also it occurs to me I've been meaning to put subframes on for ever and keep forgetting. I'll get some full length subframes on too as I hear that helps.
 

98 Saleen Cobra

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I would look into a drag oriented rear setup, NOT from MM. Maybe a double adjustable rear shock from Viking or QA1
 

98 Saleen Cobra

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Well I can only go off of the IRS car that AED has done that I know about. All of them ran QA1 or Viking.. They weren't coil overs either. The front setup doesn't play AS big of a role as the rears. But I know that the D/A ones are the ones to have. All the cars were on stock rear springs too.

If you're looking at front setups I would look into AFCO's front coilover setup. The big $$$ guys run Menscar's up front and rear, but then you're looking into like 3k worth of shock/struts and springs
 

MalcolmV8

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Wow so they just switched shocks and left the stock springs and it hooked? I've heard of Menscar but without having a good knowledge of it I'm not up for a $3k test.
 

bubblehead93

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H&R race springs or even the stock coupe springs are good enough... the rear shock is where it is at... if you want to stay stock spring position, go with the Viking B225, it is their smooth bore, double adjustable for the IRS... I now run QA-1 coil-overs in the rear for drag racing... note MM runs a 2.25" spring in the rear on its coil-overs... The QA-1 is a 2.5" spring, it is a tight fit in the stock shock pocket and requires some minor clearancing at the factory pinch welds... AFCOs are a no go in the rear, they use a 2.625" spring on its coil-overs, it would require significant re-working of the factory shock pocket... Hope that helps...

r/
Andy
 

bubblehead93

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Oh, I run DA coil-overs front and rear (QA-1s)... my experience was dialing in the rear first (start with their recommended front C/R settings and leave them for starters) for best 60 ft... then once you have the rear dialed in, start playing with the front... you won't see much by tuning the front... on the IRS its seems to be mostly in the rear with the front allowing you to only shave a few hundredths off (maybe, to be fair, the changes where never that statistically significant given the consistency of my driving, lol)... hope that helps...

r/
Andy
 

bubblehead93

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Last thoughts, when I was researching this I reached out to MM (I was also buying their coil-over kit to convert my MM2 race strut/shocks for auto-x).. they were a huge help sorting through the various drag shock offerings... to include brands they do not carry... we discussed AFCOs, QA1s, etc... give them a call...

Also, you will not find a shock application in the QA1 catalog labeled 99-04 cobra IRS... I matched the compressed and extended lengths of the stock shock and found a close equivalent... if your interested PM me... I'll hunt around a bit, I know I have the info handy somewhere...

r/
Andy
 

MalcolmV8

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Thanks Andy. That helps tremendously. If I stay with the stock rear springs I should try and find a set that has not been cut. My rear tire and fender are pretty close right now and if the car does squat properly I'll be in for some rubbing.

I looked at the Viking B225. That looks like a great drop in replacement shock. Looks like it will just bolt right in without doing much of anything. That's great.

I then looked at the QA1 from your other thread and I found this on Summit's site.
https://www.summitracing.com/parts/qa1-dd701

I like that option because its a coil over shock and at a later time if I decide to ditch the factory springs and go coil over I already have the shock and just have to add the spring on it. However the top is not a stud like stock. It's a round bearing setup. I don't think that's the right one. Your picture looks like you had found a QA1 coil over with a stud mount on top?
 

03Steve

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I've run the 295/55. IMO it's a shit rear tire for the combo.

For struts and shocks I use the Bilstein drag versions. I saw a very good improvement with them over the other combos.
 

bubblehead93

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sorry, i'm dense, you were asking about the rears... you need to buy a couple bits to convert them...

QA1 SIB110SDM converts them to studs at the top and SIB10T-102PK converts the base to a 5/8" ID spherical bearing so the factory shock bolt works....

The Viking is the cheaper route, just no way to go coil-over later...

~$615 for the QA1 setup versus ~$380 to go the Viking route...

r/
Andy
 

R3dfireCobra

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Wicked46 can hook you up both front and rear if you go Viking. I just dropped the rears in mine and its honestly an hours worth of work to do both. Waiting on the fronts to come in. But what I difference already, I am probably 100hp shy of you but ive regained a lot of traction and that's not even dialing it in yet. Mickey Thompson DR's 275 on 15" wheel, H&R race springs, and FTBR on an IRS rear. Front is tubular and coil overs on the factory bilstiens. Also, battery in trunk and no front sway bar.
 

MalcolmV8

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Wicked46 can hook you up both front and rear if you go Viking. I just dropped the rears in mine and its honestly an hours worth of work to do both. Waiting on the fronts to come in. But what I difference already, I am probably 100hp shy of you but ive regained a lot of traction and that's not even dialing it in yet. Mickey Thompson DR's 275 on 15" wheel, H&R race springs, and FTBR on an IRS rear. Front is tubular and coil overs on the factory bilstiens. Also, battery in trunk and no front sway bar.

That's great news to hear. Yes I chatted with Jon already about the Vikings and he's looking to see if he can get QA1s as well for price comparison.
I'm glad it made a big difference for you. That's what i'm hoping for.

Andy, I see qa1 makes a bolt in shock/coil over for IRS cars now. You can buy it without the springs too and add them later. I don't have the part #s or links on me right now but I'll post it up later. I found them last night. They're not cheap either.
 

apex svt

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Wicked46 can hook you up both front and rear if you go Viking. I just dropped the rears in mine and its honestly an hours worth of work to do both. Waiting on the fronts to come in. But what I difference already, I am probably 100hp shy of you but ive regained a lot of traction and that's not even dialing it in yet. Mickey Thompson DR's 275 on 15" wheel, H&R race springs, and FTBR on an IRS rear. Front is tubular and coil overs on the factory bilstiens. Also, battery in trunk and no front sway bar.
How is the no front sway bar life? I'm going to ditch mine when I put the arb in real soon here. Is it real noticeable on the street?
 

R3dfireCobra

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How is the no front sway bar life? I'm going to ditch mine when I put the arb in real soon here. Is it real noticeable on the street?
Works great for allowing the rear to squat. Handling wasn't affected too much either. I thought it would be much worse actually. Idea is to get as much weight off the front and/or put it on the rear. You want the irs to squat and stay there.

Sent from my SAMSUNG-SM-G935A using the svtperformance.com mobile app
 

MalcolmV8

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I found a set of convertible rear springs. They have a softer spring rate than the coupe. Has anyone swapped them in for more squat in the rear?
 

702lightning

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Qa1's front and rear, drag springs up front, no front sway bar,stock springs in the rear. This combo worked well for me until i went to a solid. Hit up Broke7 he's also got some great input he runs a bag in the right rear to help tq deflection
 

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