This structure makes it difficult to assemble in automobile production plants, high cost, poor reliability, and when the car is maintained at the maintenance point, it is also necessary to clean, oil and adjust the bearing. 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 gradual expansion application trend. Car hub bearings used to be the most used in pairs of single row tapered roller or ball bearings. With the development of technology, car wheel hub unit has been widely used. The use range and usage of hub bearing units are growing day by day, and have now been developed into the third generation: the first generation is composed of double-row angular contact bearings. The second generation has a flange for fixing the bearing on the outer raceway, which can be simply fixed on the bearing sleeve to the wheel shaft with a nut. It makes car maintenance easier. The third generation hub bearing unit adopts the combination of the bearing unit and anti-lock brake system ABS.