DAY 1
I just bought a used 1998 M Roadter with 82K miles. While driving the car as you approach 40MPH you start to hear a loud noise coming from the rear. My first impression was that it was the tires.

DAY 2
Just bought a new set of Kuhmos all around, but the noise is still there. I let the mechanic take it for a test drive and he "guesses" that the noise is coming from the left rear wheel bearing.

My question is...sound plausible or is there another possible cause?

Thanks!

Elias

I'd jack up that side and spin the wheel and listen and see if you hear anything. Also push on the top and the bottom of the wheel when jacked up and see if there any play in the wheel while trying to push back and forth. If theirs no noise or play then its most likely not the wheel bearing.

I'd then start to check the rear subframe bushing, I've heard that these tend to go bad. and if its a 98 and they never been changed it might be time...

Link to more info on this:
http://forums.bimmerforums.com/forum/showthread.php?t=601292

Good luck with it...

Check the rear subframe. This tends to crack inall Z3's and Z8's. On Bimmerforuns you can do a search and find plenty of info. The best fix is sold by Randy Forbes which is even recommended by BMW dealers. If this is infact your problem.