Originally Posted by Seattle S65B40
PROBLEM SOLVED: pebble in the brake rotor, or so I was told. Definitely a pebble somewhere in the RR brake. Cheers to Seattle BMW for coming through...
I'm glad my diagnosis was wrong. The sound was precisely the same as my e-brake problem. But, having had stones caught in there before, I know it can generate the same sound, since both involve something hard brushing against the dust shield.