F451

Hey guys,

I'm looking for some troubleshooting steps to track down a shimmy on my '88 S4. If anyone has any tips, or can point me to a diagnostic how-to, I'd appreciate it.

Symptoms: around 45 mph or so I can feel a back and forth shimmy through the steering wheel. Around a steady 50 mph or so, its enough to shake my arms just a bit. Its not out of control, but its noticeable and has me concerned. Once up to 60 mph or so and over, it smooths out so you can barely feel it. Under 45 or so, can't really feel it.

More data:

• Just installed new front tires/wheels, it never did this before the install - more on this below.
• Front end alignment for toe-in was done about 1.5 yrs ago, camber was not adjusted but I recall it was not far off. Rear wheel alignment was spot on.
• But, by looking at the front end alignment now, it appears that the wheels are "toed out", I am wondering if this would cause the wider tires to hunt back and forth while trying to stay on center.
• Age of shocks is unknown, they seem to be in fair condition, but its entirely possible that the are the original shocks.
• Steering rack is leaking from seals in rack.
• Steering rack mounts are worn and there is a small amount of movement there.
• There is play in the steering wheel, maybe 1/2", its not loose, but you can feel it. This was there prior to the new wheels/tires. It hasn't changed with the new install.
• Wheel bearings are tight, no movement at 12 and 6 o'clock push/pull test.
• Not sure of condition of tie rod ends, they felt tight last time I was under there, but I'm sure they are old, probably worn.

New wheels/tires info:
Just installed 265/35 - 18 Kumho SPT's on the front, on 18x10 ET65 wheels (replaced old 245/40 - 18 Pirelli P7000's on 18 x 8.5 ET52 wheels).

Had the wheels/tires balanced when mounted this weekend.

As far as I can tell, the wheels are true and straight - I did a simple check of jacking the wheels off the ground, put a fixed object near the tire tread (1/16" away) and spun the tire. The tire ran true. Next put the fixed object by the sidewall, same results. Next put the fixed object next to the rim edge, same results.

More below...

F451

Some simple testing that I did to try to determine if one of the front wheels/tires was causing the problem for whatever reason:

Removed new wheel/tire on left side, re-installed old wheel/tire. Kept new wheel/tire on right side. Took test drive - shimmy almost completely gone, was hard to detect, felt pretty much like it did prior to new wheels/tires install. Was then convinced it must be the new left side wheel/tire, so:

Re-installed new wheel/tire back onto left side, put old wheel/tire on the right side. Took test drive. Same results, very little to no noticeable shimmy!

Thinking perhaps I had mis-installed the new wheels (don't know how you would do that, but what the hell), I put them back on to test them again, and sure enough, the shimmy is back.

So, while it could be that the new wheels and tires are the cause, perhaps they are not balanced correctly, or are out of true, it doesn't seem to be the case since when one of them is installed, the shimmy disappears.

F451

I am wondering if the new wider 10" tires with the new offset are exacerbating the effects of the worn steering and suspension parts?

It would seem to be so as when any combination of the new and old wheels eliminates the shimmy completely, or almost completely.

So, before I start throwing new parts at it, I'd like to try some type of methodical troubleshooting process, going from biggest impact area, down to least impact area.

Additionally, I realize I will need to replace all of my worn parts in order to tighten everything up, but I just can't afford to do it all at once at the moment.

F451

Question: with having a relatively loose steering rack make an alignment at this time a waste of money?

I'm planning on getting the alignment after I install the solid rack mounts, I'm very curious to see if they eliminate the shimmy, along with an alignment.

Tom. M

Check your tie rods. I had a similar situation on my 87. The tie rod was worn (ball portion at the rack) and when the car was up in the air and the boot pulled away it was obvious.

Cosmo Kramer

Yes, it will be too hard to get it into spec with that kind of play.

Were the tires you put on brand new? Maybe a broken belt?

Mrmerlin

from your post i would suggest that you inspect and fix all of the worn pieces in the front end
rack leaks, worn bushings, possibly worn inner/outer tie rods, worn B joints?
Extra wide tires, also pay attention to ride height, and the shock condition.
Spin the wheels and look for bent inner portions on the bead area.
What is your purpose for the wide tires??

F451

Thanks Tom, I will check that and report back.

F451

Yes, tires are brand new. Wheels are used, but from what I can tell, they are straight and true. Also, installers did not note anything wrong with the wheels when balancing them, although I did not specifically ask about the rims.

I am planning on bringing the wheels/tires back up to them to have them double check the balance and to ask them specifically if they can determine if the wheels are true.

Hopefully that can eliminate those variables.

Leon Speed

Did you say 265 on the front?? Wow that's a lot.

My experience with new tires, especially wider new tires, is they grip like hell and tend to follow the grooves in the road more, so all play you have on the suspension and steering is very noticeable. When I changed the upper A-arms, shocks, steering rack bushings and tie rods, plus alignment, it was solved.

F451

Yes, I am planning on doing all of the above, but cannot afford to do it all at once (not working right now), so would like to the items that have the biggest impact first, and then work from there.

Ride height is on the low side of spec on the front, hi in the rear by I think 12 mm or so, something like that. Shocks are old I am sure, but they actually seem to work pretty good as far as I can tell. Not a lot of wallowing, good predictable compression and rebound control. No leaks that I can see.

I haven't checked the inner portions by spinning yet, so will do so. A quick inspection when they were off the car did not show any obvious flat areas, big dents, etc, but spinning them to confirm does need to be done.

Looks, and I have 10's in the back and like the idea of having matching tire size all around.

Ok, thanks for the input. I'll do some home work here and report back.

F451

Yes, I went from 245's on 8.5" wheels, to 265's on 10" wheels.

And I had run a test with the 265's up front using the 265's that I had on the rear of the car mounted on 10" wheels, and with the old Pirelli's, they worked fine up front, no shimmy.

But I think you're right that the new tires are gripping like hell like you said, and of course that would highlight any problems with the played out suspension and steering bits.

It just surprised me how much of a difference there is.

atb

A day out at the track in Spokane will clear that right up.

Tampa 928s

Before my brother went up north for the summer I was working on his 86.5. After I got it running he said he would hit a bump and the steering wheel would shake in his hand. I looked briefly but nothing seemed really loose so when he gets back I need to fix what ever is wrong. Anyone have these symptoms before and got a quick diagnostic on this.

F451

Enabler!

Hey man, I would LOVE to go, but do you really want a shimmying, oil oozing, steering rack leaking, needs a tb belt change, rip in my center console cassette box cover, S4 wobbling around the track with you guys?

Yeah, I know, the messed up center console lid is the deal breaker.

But hey, at this point I'm shooting for next spring.