I need a little help figuring this out on my wifes e39 530i. After a recent tire puncture the front end developed a slight vibration after several miles. I took the car to have the tires rebalanced. There was a slight improvement but I really didn't trust the shop I took it to. Several weeks later I took it to a more reputable shop. They rebalanced the tires and checked the alignment. Again, a slight improvement. I then removed the front rotors and had them turned. Bingo!! Everything was great. Here we are 5 days later and I'm getting my steering wheel shimmy again under braking. I'm pretty sure one or both of the rotors are warped again but can't figure out why. My wife is certainly not hard on the brakes and the rotors are close to being new.
Any ideas or suggestions?
Most E39 front-end vibrations are caused by the thrust arm bushings decaying. There are other possibilities, but these bushings are either the primary or secondary cause unless they have been replaced. You can go stock, but Meyle has a heavy duty version and Powerflex makes a polyurethane setup. Or you can do the grassroots thing and fill the substantial voids in the bushing with 3M Window Weld and call it done.
As an aside, it is generally considered a bad idea to cut BMW rotors. If yours were "almost new" you're probably OK, but replacement is the preferred option.
Normally I would have just replaced the rotors but I wasn't quite sure if they were the problem or not and turning them was a quick and inexpensive way to find out. They also looked almost new as well did the pads (only owned the car for 4 months). I can't figure out though what made them warp again. I'm even careful and torque the wheel nuts down properly.
minimac
SuperDork
8/12/10 7:48 a.m.
A gorilla with an impact wrench on the lugs will warp the rotors. You may have torqued them properly, but where you took them didn't. Otherwise, what O2 said is correct.
I'd second the recommendation to take a look at your bushings - sound and vibration due to bushing fatigue is a very common E39 complaint.
