Suspension Gurus: 03 Wagon, Rear end float

[kidatari]

I'm trying to help my friend Dave diagnose a problem with his recently purchased 03 WRX wagon. It is completely stock with 30k miles, with the exception of Deede's Tarmac 2s with some very well worn 225/45R17 Azenis which we installed last night.

A little bit of history: The car is a salvage, from what we can tell the front end was pushed in a bit, and the driver's side quarter panel has some bondo work. Everything else looks straight, nothing appears to be tweaked other than the front end where the bumper mounts up. Deede mentioned that it might be Debbie's old car, but I have no clue on that situation.

What we checked: The alignment was verified at Les Schwab, nothing has been modified from the stock settings. Everything checked out okay on their lazer alignment rack. We did a quick visual inspection last night when we installed the Tarmac 2's, and I didn't see any glaring problems. The gap between the sidewall of the tire and the strut was about a finger and a half on the right side, and I couldn't quite fit my finger in on the left side. Lugs are tight, tires are all air'd up to around 36psi.

Now the issue. While driving around, the car's rear end will get really light. I rode in the car this afternoon, and I noticed it sitting in the passenger seat. Dave said that he had the car up to about 120mph, and then all of a sudden the rear end got really loose. He said it got worse when he tried to brake, and he had to keep alternating the gas and the brakes to keep it in line. The car also acts odd over road gaps like expansion joints, but I can't really explain it.

We're both kind of stumped as to what the issue is. This is starting to go beyond my realm of suspension knowledge at this point. My thought is that there might be a shock problem.

Does anyone have any input?

[MPREZIV]

I would say it could possibly be the dampeners, (struts) or even some trailing/lateral link bushings in the rear end. Maybe check the links for play/worn out bushings?

[Dean]

Worn dried azenis feeel weird, and will grab every road imperfection.
Did it have the issue with the stockers?
What is the ride height (Fender to wheel center on each corner?
Did you look at the sway bar, end links, etc.
Did they give yoy a printout of the alignment? Did it include setback, etc..

[Kevin M]

Originally Posted by kidatari

The gap between the sidewall of the tire and the strut was about a finger and a half on the right side, and I couldn't quite fit my finger in on the left side. Lugs are tight, tires are all air'd up to around 36psi.

If the tire-strut gap is very different, than there are going to be really weird dynamic camber/toe issues. I bet the toe control bolts are in way different positions too.

Also, it's definitely not Debbie's car. Hers was rear-ended, and I think it was an '02 anyway.

[kidatari]

Worn dried azenis feeel weird, and will grab every road imperfection.
I know this, and this is definately different.

Did it have the issue with the stockers?
He isn't sure. My thoughts are that since the sidewalls on the Azenis are so stiff, it exascerbated any problems that it had before

What is the ride height (Fender to wheel center on each corner?
I can get that info tomorrow.

Did you look at the sway bar, end links, etc.
I gave everything the once-over when we were swapping the wheels.

Did they give yoy a printout of the alignment? Did it include setback, etc..
Dave has the printout, not sure if it included the setback, etc. He'll have the printout at work tomorrow.

[sti deede]

This one was rear ended too.

[Joeyy]

I run an Azenis for autoX on a 05 wagon. I have a heavy grooved road to drive on my way to Stead and they feel "crazy". I couldn't amagin what they would feel like on that road at 120mph. I'd go with something simple like putting your other tires back on. Well, thats my 2 cents worth of knowlege.

[kidatari]

Originally Posted by BAN SUVS

If the tire-strut gap is very different, than there are going to be really weird dynamic camber/toe issues. I bet the toe control bolts are in way different positions too.

There isn't a giant difference in the strut gap, but there definitely is a difference.

To me, the problem sounds like bump-steer. Almost like when the weight transfers to the front of the car, the rear toe changes.

According to the Les Schwab guy (yes, yes, I know...) everything is straight and no alignment mods have been done since the car was new.

[Kevin M]

Originally Posted by sti deede

This one was rear ended too.

Josh sort of forgot that part. If it was, it's way easy to bend the rear subframe, or just shift it on its mount points enough to do goofy things.

[Kevin M]

Originally Posted by kidatari

There isn't a giant difference in the strut gap, but there definitely is a difference.

To me, the problem sounds like bump-steer. Almost like when the weight transfers to the front of the car, the rear toe changes.

According to the Les Schwab guy (yes, yes, I know...) everything is straight and no alignment mods have been done since the car was new.

Egg zachary. If the toe control bolts aren't more or less the same position-wise, then the swing axis of the rear wheels is not parallel (or more not parallel?) than it is supposed to be.

[kidatari]

Originally Posted by BAN SUVS

Josh sort of forgot that part. If it was, it's way easy to bend the rear subframe, or just shift it on its mount points enough to do goofy things.

The car might have been rear ended, we're not entirely sure. But if the rear subframe was tweaked, wouldn't the car's alignment be off, or have alignment settings maxed out to compensate for damage?

[kidatari]

I sent Dave a link to this page, hopefully he registers and adds in his own two cents.

[Dean]

alignments can be made fine, even with a bent frame, but that doesn't make the frame not bent.

Corner heights will give us some info, as will the rest of the alignment info if it is there, or and they bothered to do it.

Does the car look square from all angles? Bumper and underbody sill/joint heights at the jack points might help as well.

[Joeyy]

Can you run the car thru car fax and see what kind of collisions its been involved in?

[Kevin M]

They may or may not show up. My car was hit 3 times, and the only one that will show up is the last one.

[sybir]

Josh, I replied on icrub, but the differing gaps between wheel and strut body are jsut not right. I'd wager either the pickup points are tweaked, a lateral link is bent, or the strut body itself is twisted a bit.

[kidatari]

That's what I'm thinking at this point.

[kidatari]

I just got off the phone with Dave. We'll be pulling all the wheels off and taking measurements and whatnot tomorrow evening. I'll also post the alignment sheet tomorrow. Thanks for everyone's input.

[kidatari]

Update- We got the car up on the lift today, it looks like the driver's side trailing link is tweaked. We're heading down to the yard to get a replacement and swap it on tonight. Hopefully it fixes the issue.

[kidatari]

All fixed now, the driver's side trailing link was the issue. It was twisted and bent. Matching up the mounting points for the front end, the rear end was approx 1.25" off. We got it swapped out last night and now everything is gravy

Thanks for everyone's input

[Kevin M]

Sweet.