[E34] Front End Shimmy

[Randy S Whitney <rsw@xxxxxx>]

(resent as the first didn't appear to go through)

I'm hoping the list at large can help solve my problem.

I've finally developed the notorious front-end shimmy on my 1994
540i. The problem started off small, with a little shaking when
I applied the brakes between 55-45. It has now escalated to the
point where if I keep the car in a straight line at 50-55, the
whole car starts shaking, starting from a slight vibration up to
the point where I have to hold tightly on to the steering wheel 
because of the vibration.

The interesting thing is, if I turn to the left, such that I am
slightly loading up the right front suspension, the shaking 
dissipates (more on this later), though when I straighten out the 
wheel, the shaking immediately resumes.

A couple interesting tidbits that might either serve to narrow 
down the problem or perhaps give additional areas to look:

1. I recently replaced the front rotors--this would seem to rule
   out warped front discs. (The shimmy didn't appear until a few
   weeks after the new rotors were on the car) I replaced the
   OEM rotors with ATE Power Disc rotors, which seem to provide
   improved stopping power.
2. I just replaced the control arm bushings with the more solid
   750i bushings I have heard good things about. This helped to 
   tighten up the suspension, particularly on turns, etc, but 
   seemed to actually amplify the problem rather than solve it.
   [I did observe that one of the bushings that was returned to
    me had ruptured/torn, so this probably was not a bad idea
    anyway.]
3. I swapped the front and rear wheels to see if there was a 
   wheel balance/bent rim issue. When I had the wheels off the
   car, I didn't notice any visible signs of a bent rim, but
   It didn't hurt to try. This did seem to dampen the shimmy
   _slightly_, but the problem is still there.
4. When I took of the right front wheel, I noticed that the
   front strut appears to have ruptured. There was what seemed
   to be some traces of oil covered in brake dust on the inside 
   of my wheel, and there appeared to be some visible signs of
   stress where the spring rests on the strut assembly.

Could a blown strut cause the shimmy I have been observing? It
seems to make sense, based on what I've observed, but I want 
to be sure before I spend $400.00 + Labor to replace the shocks
and struts (been eyeing a set of Bilsteins for a while). What 
other things should I look at in addition to this? I've seen 
some mention of full on the car wheel balancing, but I'm not 
sure if that is the best solution--can anyone vouch for this?

Thanks in advance,
Randy.

1988 325is (sorely missed)
1994 540i 



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