Rolling bearing unit

1. Field of the Invention Two bearings are used to rotatably support the pivot with reference to a fixed shaft. The swing arm is highly precisely fixed to the pivot . The outer diameter of the outer race of the lower bearing is larger than the outer diameter of the outer race of the upper bearing . The end surface of the outer race of the outer race of the lower bearing and the outer periphery of the outer race of the upper ball bearing are used as a reference surface to fix the swing arm . The housing used in the prior art is eliminated from the structure according to the present invention to reduce the number of parts.