03-04 IRS swap info

[331eddie]

Has anyone on here done an IRS swap into a fox body?
I'm looking for some information regarding suspension options and wheel fitment. :shrug:
As for the suspension-
I have strange 10 way adj shocks with UPR's strange specific coil over kit for solid axle fox bodies.
1. Will they work on the IRS?
2. If I get strange shocks for the IRS will the fox coil over kit work with those?
3. Are the shocks in the solid axle the same length as the IRS shocks?
4. If I buy a coil over kit for the 03-04 cobra IRS, will it fit in the fox with no issues?

As for the wheels- Currently using 275/40/17s on 17x9 FR500s 22+offset.
1. Am I right with my calculations that a 17x9x40+ offset will work?
2. What offsets are being used to fit right with the IRS swap?
3. Is it easier to fit an 18x9 vs a 17x9? (due to the subframe mount on the IRS sticking out into the wheel well)
4. is there room for a 9.5 or 10 wide wheel? (17 or 18)

End results I'm looking for from this thread are-
1. Easiest way to get coil overs to work with the conversion.
2. What wheels will fit without going less than 9" wide. :??:

Thanks in advance and no worries if nobody knows these answers, LOL.
I will post updates as I find out along the way.

 

[scottL]

wheelhopper swapped an '03 IRS into his '90 GT, maybe he'll chime in: http://www.svtperformance.com/forum...0760-my-latest-project-irs-into-fox-body.html

 

[wheelhopper]

straight axle shocks will bolt up but are not the correct length for the IRS. You may have a bottoming out issue. Best bet is to get the kit for an IRS car. Once the IRS is in the fox you simply shop for '99-'04 Cobra parts for the rear suspension. I have run several types of conventional springs in the IRS and am now running a MM coil over kit specific to an IRS.

I have run the following wheels on my car

2001 GT 17x8 wheels with 245s
1998 Cobra 17x8 wheels with 245s
1999 Cobra 17x8 wheels with 255s
2003 Cobra 17x9 wheels with 255s (these rubbed on the front to much for me to use)

I run my car on a road course and you may not have some of the wheel rub issues that I have. My car sits fairly low and I drive the crap out of it.

 

[331eddie]

ScottL, Thank you!!!

Wheelhopper, Thank you as well. It was about what I thought about the suspension and will now just buy a coil over kit for IRS.
With the 255's in the rear, How close were you to rubbing tire on the inside?

My car is super low and I plan to road race it as well. Could a 275 fit back there?

 

[scottL]

I have run the following wheels on my car

2001 GT 17x8 wheels with 245s
1998 Cobra 17x8 wheels with 245s
1999 Cobra 17x8 wheels with 255s
2003 Cobra 17x9 wheels with 255s (these rubbed on the front to much for me to use)

I run my car on a road course and you may not have some of the wheel rub issues that I have. My car sits fairly low and I drive the crap out of it.

Mine has coilovers & is significantly lowered. i also run '03 17x9 Cobra wheels all the way around. Tires are 245-45's up front & 275-40's out back w/ a solid axle. Rear fenders are rolled. No rubbing issues. Front wheels stick out beyond the fenderwells but my tires tuck under them

 

[blacksheep-1]

yes...check out this link, it's extensive but does answer a lot of your questions..plus some you've never asked.

Johnny Cash Mustang project

 

[wheelhopper]

ScottL, Thank you!!!

Wheelhopper, Thank you as well. It was about what I thought about the suspension and will now just buy a coil over kit for IRS.
With the 255's in the rear, How close were you to rubbing tire on the inside?

My car is super low and I plan to road race it as well. Could a 275 fit back there?

A 275 would fit in the rear but not in the front without a wide fender kit or fabbing some custom flares, which a lot of fox body guys do for the road course. 255s will fit in the front but the problem is that a 17x9 wheel causes the tire to rub the outer fender lip under track conditions and a there is no sense going wider than a 245 on a 17x8. I also prefer to keep the same size front and rear for track use. Having a larger size in the rear causes contributes to an under steer condition.

Mine has coilovers & is significantly lowered. i also run '03 17x9 Cobra wheels all the way around. Tires are 245-45's up front & 275-40's out back w/ a solid axle. QUOTE]

No problem with 275s with a straight axle on the fox. The IRS is 3" wider than a fox straight axle and 1.5" than an SN95 or New Edge Mustang. That makes tire fitment a little more challenging.

 

[SVTORANGE]

I have done it three times thusfar.
Never have I used any suspension parts from the solid axle only IRS supension parts with the IRS.
Also used the same tire setup 17x9 and 17x10.5 with 245x45x17 on them