shimmy
 

1997 E420 with 98,000 plus miles. Through 3 sets of tires, all different manufacturers, wheel alignments, 4-wheel, and more tire rotations and balances than I can count, this car still has a shimmy that frequently, but not always, occurs in the 50-60 MPH range. It is not violent but it is definitely there. It even can be felt at times when braking. The most disconcerting thing about it is the fact that it does not happen all of the time. I have discussed this with my dealer and 3 tire stores. I have had the original Michelins,and replacement Pirellis, Continentals and Bridgestones on the car and they all do it. The wheels are not damaged and neither is the suspension. It has never been in an accident. I love this car but this shimmy drives me crazy. The brake pads and rotors have always been replaced in sets. I cannot think of anything else that I can do or have done. Does anyone know of a similar problem? Is there something I've missed? My dealer alluded to having heard of this problem before but could offer no solutions other than computer balancing, which did not work.:confused:

the drive shaft can get out of balance. THere are companies that specialize in rebuilding and rebalancing the drive shafts.

Conventional wisdom is that this should never have to be done unless the drive shaft has been damaged....

This would drive me nuts. Here are just some ideas. I had a jaguar that used to shimmy with the sunroof open and windows up. The minute I cracked open one window the shimmy went away. #2 There is suppossed to be ABSOLUTELY NO PLAY in the tie rod and bearings in my front end. Make sure this is the case with your car. Then, on a lift, take a large pair of pliers and place them around the ball joints and try to move them. If there is even 2 mm worth of play, you may have found your problem. Maybe try replacing the shocks or struts. Good luck..

Drive shaft very well could be it!! Excellent suggestion! I had a Miata that did this at exactly the same speed every time. Good indicator!!

I have the same problem. Sometimes the car is smooth, some times it ain't. If it is a balance problem it would be consistent. I suspect a worn bushing in the suspension, differential or trans. It the rubber is worn the component may shift into a position that causes vibration sometimes and then works its way back to smooth. Sounds simple but finding the real cause isn't.

How about the idler arm or the wheel bearings? I had a shimmy around this speed -- maybe a little higher. That seems to have taken care of the problem for me.

Rack & Pinion
 

I believe that it is an inherent problem with the E420. That was the first year that they went to Rack & Pinion with the V-8. I think that the shimmy was always there, but previously masked by the recirculating ball power steering found on the 400E/E420's.

If its any consolation I've spoken with many BMW techs that have also noticed the same thing with the BMW 5-Series. The 528i has a shimmy problem (rack & pinion), while the 540i does not (recirculating ball).

Had the same shimmy. Replaced tires and balanced them endlessly like you have. Replaced upper shock bushings and the car still had the shimmy. The dealer originally replaced the upper control arms and the car still did the same thing. The dealer then replaced the front lower control arm bushings and the shimmy went away. Hope this helps

Took me a while to diagnose a very similar problem. The wheel bearing on the passenger side was loose. With the wheel off the ground I could feel some play in the bearing when jiggling the wheel. Tightened the bearing until I could not feel any more play. On a test drive the shimmy was almost non existent. Tightened the bearing just a little more, not overtight!, even though I couldn't feel any play from the previous tightening and now no vibrations.
Can a wheel bearing be damaged from being overly loose?

my 2 cents :)

Dan