Scalloping along one edge, typically the inner edge, tends to happen as a result of problems deeper in the suspension. Bad wheel bearings can cause edge scalloping, but so can bad ball joints, bad steering or sway-bar end links, damage to the steering linkage or control arm, and severely damaged suspension bushings. This kind of wear happens because something in the suspension is bouncing or vibrating when that wheel is compressed during cornering. Edge scalloping could be a sign of impending disaster, so have it checked out immediately.