The wheel hub bearing is one of the key parts of the car. Its main function is to bear weight and provide precise guidance for the rotation of the wheel hub. It is usually located at the connection between the five-pointed axle and the wheel hub, and is also called the hub unit. The wheel hub bearing consists of an inner ring, an outer ring, rolling elements, a cage and a sealing ring. The bearing steel ball flips in the inner ring, the outer ring or the flange raceway to achieve the driving of the car.