Alignment problems with IRS Cobra

[1999SVTVert]

Hey guys-
I just got some new tires put on my 99 Cobra and decided to get a 4 wheel alignment done while I had it in- Some uneven wear on the old tires. Car has stock springs and struts/shocks.

Well I just went to pick it up and the guy said they had some problems getting the car to align. He said that they were not able to get enough camber put into the front tires, they are out of room for adjustment in the towers.

Problem is that now when you let the clutch out from a light, you can feel the car shift to one side, and when you get off the gas or push in the clutch the car shifts to the other side. They are going to work with the alignment again, but I wanted to see if anyone here had dealt with this before or if there is anything I should ask them when I go back to check it again.

Does anyone know the correct settings recommended for the IRS Cobras that they should be shooting for? Right now I would be happy if they could just get it back to where it was before I took it in.


Thanks!
Adam

 

[s9v9t]

Have you ever checked your rear subframe bolts? The front bolts are supposed to be larger diameter than the rears. Ford goofed on a large percentage of early IRS mustangs and put the smaller bolts front and rear. This can cause the subframe to shift slightly on the car. Usually you will get a "clunk" if its bad enough - and maybe some tire wear and spooky handling issues. I had this issue on my '99 a couple of years ago. I checked my car, and sure enough I had the wrong bolts. I got new ones thru Maximum Motorsports - Installed them - my clunk disappeared! Just a thought - worth looking at if you never checked it.

 

[1999SVTVert]

That is one thing I hadn't thought to check- I replaced the IRS bushings long ago with the MM red ones, but never checked the bolt diameters. I'll have to pull them this week and check.- Thanks!

 

[s9v9t]

Actually, you don't have to pull them out to check the bolt diameter. If you crawl under the car you can see the end of the bolt extending thru the chassis.

Rear subframe bolts are 12mm, fronts should be 14mm. Take a 12mm open end wrench and see if it fits over the THREADED portion of the protruding front bolt. If the 12mm fits you have the wrong bolts!

Note that it is important that you measure the threaded portion - as the bolt tapers at it's end.

Correct bolts are available from MM for around $20.00 for the pair. As you probably know MM has a great website, with tons of tech stuff related to the products they sell. I believe they have detailed bolt measurement and replacement instructions on there too.

Another quick thing to check are the rear sway bar end links. I hear they are a common failure item on IRS cars. That can definately mess up your cars handling. I had a broken one of those on my car too.

Just curious; do you feel the upgraded bushings were worth the effort? Which ones did you change - Just the subframe bushings or everything? My car has almost 75,000 on it, and I have been thinking about rebuilding the IRS. Do the harder bushings make a difference?

Good Luck with you car!

Mike

 

[1999SVTVert]

Mike-
I replaced a bunch of bushings all at once- I replaced the front swaybar bushings (MM), front endlink bushings(MM), rear urethane subframe bushings(MM), IRS heavy duty crossmember with urethane bushings (Steeda) and IRS swaybar bushings(MM).

I think that the upgrades were worth it- IRS seemed to definitely hop less, and felt a lot more solid. (that is until my latest alignment/bolt?) issue. Steering seemed to be a lot more precise up front as well. I don't drive my car very hard, but I could definitely tell a difference. My rubber bushings seemed to be pretty worn/loose all around.

By the way, I do have the incorrect 12MM bolts up front in the IRS. I didn't even check them before because everything was asymptomatic. Thanks for the reminder and I have the correct bolts on the way. Fingers crossed that it is the root of my current problem. I'll have to check on the rear swaybar endlinks as well.


Adam

 

[s9v9t]

Adam,

Thanks for the feedback on the bushings - I'll have to look into that.

Getting the new bigger bolts to line up is kind of a bitch, so if you're prone to freak-outs be sure to pack some extra patience. Considering the other suspension work that you have already done, I'm sure you'll be ok.

It kind of pisses me off that Ford didn't do a recall on this like they did with the spindles, especially on a high-end model. I guess maybe they didn't want any more bad press after the horsepower fiasco on the '99's, and the spindle recall. Oh well.

Hope this solves your problem. Let us know how it tures out!

Mike