So what are some of the clues that a rear wheel bearing is going bad? After some spirited driving (track day) I get a faint high pitched ocilating howl from the left rear area of the car. It dosen't make noise when I'm just out driving around.
I just rebuilt the brakes (including new rotors) and adjusted them correctly so I'm fairly sure that's not the source.

Any suggestions or comments? Thanks in advance!

rear wheel bearing is more of a grinding noise.
easy test, drive it for a bit without heavy braking,
get out of the car and feel the temperature of the middle of your wheel.
if you burn your fingers, the bearing is toast.
they get really hot when they start going bad ...

Andy

Wheel bearing is bad Greg.

Unbolt the caliper (let it hang from a bungie cord) and grab the wheel like you would be checking the front wheel bearings.

The left side normally goes out first do to it being the drive side.

B