A bicycle hub is provided with a hub axle, a hub shell and a pair of bearing units. Each of the bearing units has an inner race supported on one axle end of the hub axle, an outer race threadedly coupled to an inner tubular surface of the hub shell, and a plurality of first rolling members disposed between the inner and outer races. Preferably, a first stopper ring is coupled to one of the first inner and outer races to form an axial abutment that is arranged to contact the other of the first inner and outer races to prevent axial separation of the first inner and outer races prior to installation of the bearing unit between the hub axle and the hub shell.