2003 Cobra IRS on 2001 Cobra

Bluehorse · Jan 10, 2004

I've read a few comments on this board about using the 03's IRS on a 2001 cobra, but I would like know if someone has used the entire 03 IRS set on their 01 cobra. Does it fit and eliminate the wheel hop with tires up to and including drag radials?
Also, what does the entire 03 IRS setup mean? Is it shocks, springs and brace, or is there more to it than that?

grey03cobra · Jan 10, 2004

Bluehorse said:
I've read a few comments on this board about using the 03's IRS on a 2001 cobra, but I would like know if someone has used the entire 03 IRS set on their 01 cobra. Does it fit and eliminate the wheel hop with tires up to and including drag radials?
Also, what does the entire 03 IRS setup mean? Is it shocks, springs and brace, or is there more to it than that?

They are the same IRS. The only difference in the rear suspension on the 03's is a cross brace added to the IRS help prevent wheel hop. Part of what helps are different spring rates on the 03's, as well as Bilstien shocks. The 03s also have slightly stronger half-shafts.

I had a 99 Cobra (same IRS as the 01) and I installed polyeurethane bushings and Steeda springs and completely eliminated wheel hop with my street tires (I never tried running with DRs).

With my 03 I've run BFG DRs with no wheel hop what-so-ever. I currently have Steeda competition springs and polyeurethane bushings.

Hope this helps

amargari · Jan 11, 2004

There are actually a couple of other differences.
1. The flange connecting the diff to the drive shaft is different. The 03 is beefier.
2. The rear tie rod mounts in a different location. It is either lower or higher by a little bit. I can't remember which.
3. Also some of the bushings are stiffer than the older ones.
4. There is also a rumor that the rear knuckle is different.

There may be others but they haven't been confirmed.

Bluehorse · Jan 11, 2004

grey03cobra said:
They are the same IRS. The only difference in the rear suspension on the 03's is a cross brace added to the IRS help prevent wheel hop. Part of what helps are different spring rates on the 03's, as well as Bilstien shocks. The 03s also have slightly stronger half-shafts.

I had a 99 Cobra (same IRS as the 01) and I installed polyeurethane bushings and Steeda springs and completely eliminated wheel hop with my street tires (I never tried running with DRs).

With my 03 I've run BFG DRs with no wheel hop what-so-ever. I currently have Steeda competition springs and polyeurethane bushings.

Hope this helps

Yes this helps a lot. Thanks.
So, it looks like it's, springs, bushings, shocks and brace.
By the way, 11.24 at 124, nice time and speed.

Bluehorse · Jan 11, 2004

amargari said:
There are actually a couple of other differences.
1. The flange connecting the diff to the drive shaft is different. The 03 is beefier.
2. The rear tie rod mounts in a different location. It is either lower or higher by a little bit. I can't remember which.
3. Also some of the bushings are stiffer than the older ones.
4. There is also a rumor that the rear knuckle is different.

There may be others but they haven't been confirmed.

Hmmm, I suppose these mods may also impact wheel hop.
You're right about the above and the tie rods being in a different location. Not sure what that does.

Still, I think the vast majority of the improvement is in the springs, bushings, shocks and brace. Any of you guys disagree?

Steel City · Jan 11, 2004

Bluehorse said:
I've read a few comments on this board about using the 03's IRS on a 2001 cobra, but I would like know if someone has used the entire 03 IRS set on their 01 cobra. Does it fit and eliminate the wheel hop with tires up to and including drag radials?
Also, what does the entire 03 IRS setup mean? Is it shocks, springs and brace, or is there more to it than that?

If your going to go to all of the trouble, why not the live axle?

Bluehorse · Jan 11, 2004

Steel City said:
If your going to go to all of the trouble, why not the live axle?

I've given that some thought, but like the IRS other than the wheel hop.

SVTCobra2001 · Jan 12, 2004

For the amount of money that you would spend on the purchase and swap of the IRS, you could just build up your 01' IRS and it would be better than if you swapped it. Get some Delrin Bushings, upgrade the H-Shafts, put in the brace, and new shocks and struts. The purchase of teh 03' IRS will set you back just a bit less than all the parts to make the 01' better.

Bluehorse · Jan 12, 2004

SVTCobra2001 said:
For the amount of money that you would spend on the purchase and swap of the IRS, you could just build up your 01' IRS and it would be better than if you swapped it. Get some Delrin Bushings, upgrade the H-Shafts, put in the brace, and new shocks and struts. The purchase of teh 03' IRS will set you back just a bit less than all the parts to make the 01' better.

Yes I agree.
Are you sure the above works well together, handles well and eliminates wheel hop?

hotrodman · Jan 12, 2004

Bluehorse said:
I've read a few comments on this board about using the 03's IRS on a 2001 cobra, but I would like know if someone has used the entire 03 IRS set on their 01 cobra. Does it fit and eliminate the wheel hop with tires up to and including drag radials?
Also, what does the entire 03 IRS setup mean? Is it shocks, springs and brace, or is there more to it than that?

i have 99 cobra with IRS i got the eibach prokit it stoped all my wheel hop completely with stock shocks still on car 51,000miles stock springs hop hopped like a rabbit get the springs you wont be disapointed

psnous · Jan 12, 2004

I thought the size and number of splines of the halfshafts were different too?????????????

Bluehorse · Jan 13, 2004

hotrodman said:
i have 99 cobra with IRS i got the eibach prokit it stoped all my wheel hop completely with stock shocks still on car 51,000miles stock springs hop hopped like a rabbit get the springs you wont be disapointed

I think what you're suggesting is springs and brace alone will go a long way towards solving the wheel hop issue. I'll look up the eibach prokit. Thanks

psnous · Jan 13, 2004

Hmmm, I dunno I can get a pretty good deal on a 03 IRS and I think I'm gonna do the swap as well

SVTCobra2001 · Jan 14, 2004

Bluehorse said:
Yes I agree.
Are you sure the above works well together, handles well and eliminates wheel hop?

I never had a big wheel hop issue on my 01' to start with> I think that upgrading the bushings to Delrin or Alum. is the best upgrade. Or at least from that I have "SEEN" Saw some photos of before and after the install of Delrin and it was a definite upgrade.
Now on my 03' the wheel hop is crazy. I couldn't believe the differance between the 01' and the 03'. Just not sure what route I am going to take to fix the issue yet. I might be completely rebuilding the whole car setting it up for OT events. We will have to see.

Firme · Jan 14, 2004

to cure wheel hop....(5 things (6 if you have a lot or money))

1. Stiffer springs
2. Higher Dampening Shocks
3. IRS Brace (03 cobra has this already)
4. Steeda Urethane Differential Bushing..
5. Maximum Motorsports Urethane IRS Bushing..

6. TORSEN RACEMASTER T-2R (TYPE 2R)

Delrin Control arm bushing would help conrnering....

Delrin on the Differential or the IRS itself are a BAD IDEA IMO

Bluehorse · Jan 14, 2004

psnous said:
Hmmm, I dunno I can get a pretty good deal on a 03 IRS and I think I'm gonna do the swap as well

It seems that way to me also.
From Ford parts network I see the following prices:
Brace 79.99
Springs 46.99 ea
Shocks 66.99 ea
I have not priced the bushings. Total for the above would be 305.95 for the complete swap.
You have a place that give better pricing?

Bluehorse · Jan 14, 2004

SVTCobra2001 said:
I never had a big wheel hop issue on my 01' to start with> I think that upgrading the bushings to Delrin or Alum. is the best upgrade. Or at least from that I have "SEEN" Saw some photos of before and after the install of Delrin and it was a definite upgrade.
Now on my 03' the wheel hop is crazy. I couldn't believe the differance between the 01' and the 03'. Just not sure what route I am going to take to fix the issue yet. I might be completely rebuilding the whole car setting it up for OT events. We will have to see.

That is interesting. My 01 wheel hop almost any time I press hard on the accelerator in first. I still have the stock tires. Wet whether is bad also.

So your 03 wheel hops. I'm not sure what to think now?

psnous · Jan 14, 2004

Bluehorse said:
It seems that way to me also.
From Ford parts network I see the following prices:
Brace 79.99
Springs 46.99 ea
Shocks 66.99 ea
I have not priced the bushings. Total for the above would be 305.95 for the complete swap.
You have a place that give better pricing?

No there's just alot guys around here making big power in 03 Cobras and are swapping in live axles, so there are quite a few 03 IRS' around for pretty reasonable prices, plus I can sell mine or keep it and build it up as a spare.

Lo Pony · Jan 14, 2004

The differences between the 99-01 IRS and the 03 IRS have already been stated. The rear tie rod pickup point was lowered 5mm to improve the camber/toe curve at jounce. Higher durometer bushings throughout, plus the front differential brace and revised knuckles are different. The 31 spline shafts are better than the 01 31 splines, and significantly improved over the 99's. The subframe bushings and lower control arm bushings, the differential brace, plus good shocks and springs will get you practically even with the 03 in terms of wheel hop. You can get a rear steer kit from KB and MM to cure the camber toe problem in the rear. Probably, by FAR, the most significant difference you'll make to your IRS is the addition of the KB poly subframe bushings and either delrin LCA bushings from Motion Dynamics or poly LCA bushings from KB. By FAR!

2003 Cobra IRS on 2001 Cobra

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