Wipe the grease off the hub assembly and outer bearing race with cleaning solvent and clean the bearings thoroughly with the solvent and dry them thoroughly without rotating them with compressed air. Check the inner and outer bearings, both, and especially the inside surface of the bearings, whether scratched, pitted, or excessively worn, and the insides to see whether galled, where a stroke of improper installation has probably occurred and made the bearing slide laterally and damaged it. Also, inspect the rotor surfaces, pitting, scratches, or hot spots, in case of wear marks, it is better to have the machine shop turn the rotor in a lathe to remove the imperfections, and in case, it is so badly worn, then it should be replaced.