My left rear wheel recently started making a grinding noise (right after having the rear discs replaced). It is worst at low speeds (up to 20-25 mph) and most notably, it gets much worse when cornering either left or right, especially left. It seemed to disappear a few days after having the brakes done but now it's back, and getting worse.
I can't see any visible scoring on the rotor so I don't think it's a piece of trapped grit or dirt. Any theories?