Wheel bearing's main function is to load and the rotation of the wheels provide accurate guide, it already axial load and bear radial load, is a very important components. Traditional car wheel bearings for consists of two sets of tapered roller bearings or ball bearings, bearing a combination of installation, greased, sealing and clearance adjustment is in auto production line. This structure makes it in auto manufacturers assembly difficulty, the high cost and the poor reliability and automobile maintenance in thrusters, also need to bearings cleaning, greased and adjust. Wheel bearing unit is based on standard Angle contact ball bearing and tapered roller bearings are developed on the basis of, it will two sets of bearing assembly as an organic whole, have good performance, can be omitted the pre-load adjustment, light weight, compact structure, load for large capacity, sealed bearings can advance into grease, ellipsis external wheel sealing and from maintenance etc, and has been widely used in cars, in trucks also have gradually expand trend of application.