Hub bearing (hub bearing) is the main role of bearing and provide accurate guidance for the rotation of the hub, it bears both axial load and radial load, is a very important part. The traditional automobile wheel bearings are composed of two sets of tapered roller bearings or ball bearings. The installation, oiling, sealing and clearance adjustment of bearings are all carried out on the automobile production line. This structure makes it difficult to assemble in automobile production plants, high cost, poor reliability, and the car in the maintenance point maintenance, but also need to clean, oiling and adjustment bearings. Wheel hub bearing unit is in the standard angular contact ball bearings and tapered roller bearings, on the basis of it will be two sets of bearing as a whole, has the assembly clearance adjustment performance is good, can be omitted, light weight, compact structure, large load capacity, for the sealed bearing prior to loading, ellipsis external wheel grease seal and from maintenance etc, and has been widely used in cars, In the heavy truck also has the trend of gradually expanding the application.