I should have come here for help 4 years ago, but here goes; this car is my wife's around-town car, with basically normal family-type driving, and averaging 10K-12K miles per year (currently 144,700 miles). It has 5-spoke wheels which I don't think were original, though they are factory wheels (tire size 225/55R-16); similar to the "M Parallet Spoke" wheels that Bavarian Autosport shows on their site. When we bought the car, Car Tender (great indy shop) in Seattle was trying to diagnose a front end vibration/steering shimmy that occurs at 45mph, then disappears as we speed up or slow down. The "sweet spot" for this is only about 2-3 mph wide. They had checked wheels, tires and suspension without success. This had continued occasionally after we bought the car. In May 2006 at 123K, we bought new tires at Les Schwab, with spin balancing, and the problem disappeared almost completely - until we had the tires rotated, and it started up again. We rotated back, and again almost disappeared. It has been liveable since then, until yesterday when we had our local mechanic replace brake pads on all 4 wheels. Tires were replaced on the wheels they had been on, but the vibration/steering shimmy is suddenly back with a vengeance, now starting at about 35mph, and going almost to 50 mph. After test driving the car this am, we rotated front to back again, and though a little better, still much worse than before, and still with the expanded "sweet spot" range. This happens both accelerating and decelerating. We've had the suspension checked to see if anything is loose or missing, without success, and a wheel alignment at 127K, with no discernable improvement or worsening. I am absolutely not mechanical, but between everyone who's looked at it, we are out of ideas. Has anyone run into this previously, so we can learn from your experience?
I may not have the same model as you, but I had a similar experience a year or two ago. The front right wheel would vibrate violently between 40 and 50 mph, regardless of acceleration or deceleration. The tires were rotated and balanced and the problem was almost gone (still felt a little bit of vibration but it shifted from 50mph to about 80, and it was barely noticeable). And, after a while, it came back again. The shop replaced the control arm and bushing and it was fine ever since.
Shimmy I agree with az3579. My car also has the death wobble at 45 ish. It is horrible on braking. I know I need the control arm bushes but I haven't gotten around to putting them on. I also need a condenser fan and some other minor issues. I am really looking for a decent old e30 to putt around in while I reduce the driving on the e32 and fix some of her issues.
That is pretty typical symptoms for bad upper control arm bushings. They aren't that expensive (expect ~$150 each for Meyle brand) and they're about due with that many miles anyway. Now, on an E28, we'd use milled E32 750 bushings. I would expect you can use the whole 750 arm.
Just so you know, a visual inspection is very difficult. The bushings generally don't look bad at all. Manipulating them is also difficult because you have to really pry on the arms to get any movement in the bushing. It takes someone very experienced with BMWs of this vintage (early '90s and back) to tell whether they're bad or not. Ask if they are familiar with the procedure for properly torquing the bushings. [They must be tightened and torqued with the suspension fully loaded, not hanging in the air.] If they don't know, then I would seriously doubt their ability to properly diagnose the problem. Sometimes, the more obvious sign is that the ball joints at the outer ends are getting loose. Again, a visual inspection is almost worthless. You have to grip them with the biggest channel lock pliers you can find and squeeze hard. There is no 'tolerance'. If they move at all, replace them. The front suspension BMW used on all the cars at that time is very sensitive to worn parts, misadjustment, and tire and brake balance. Any of a number of things can make them shake. This is just the most common reason for the speed-related shimmy you're seeing.
