By your description, that does sound like a bad bearing. Can you tell which corner of the car it's coming from?

Ours has one or more bad wheel bearings, and I'll be jiggered if I can figure out which one it is. But the car has nearly 160,000 miles on it, so I'm just going to replace them all. I've got the parts, but am currently working on getting the tools needed for the job (and giving my back some time to heal up before diving into a job that will have me crawling around on the floor most of the day.)

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2001 X5 Sport 3.0/5-speed
1998 318ti/5-speed
1988 735i/5-speed
1984 528e/5-speed (soon to be M20B25-powered 525i!)