I took off the rear wheel (my first time doing this) in order to have the tire replaced and i also changed the rear sprocket. When i reassembled the rear wheel and spin the tire while on the rear stand i get a knocking sound as i rotate the tire. i checked to ensure nothing was rubbing, moved the tire left and right to ensure everything is tight and can't seem to find the problem. I also removed the wheel again and rotated the parts individually to figure the problem out. by the way i never removed the bearings but i can't rule them out. i have greased every moving part. any suggestions?