Hub: hub is also called the wheel ring, tire bell, wheel, is the tire inner profile support tire shape is a barrel, the center of the metal parts installed on the shaft, hub according to the length of the diameter, the width of the different size, the difference in the way of forming, the use of different materials are divided into many different types.

In the classification can be roughly divided into paint and electroplating two kinds, ordinary models in the choice of wheels mainly consider whether the heat dissipation is good, do not pay much attention to the appearance, the process is basically using paint processing, that is, first spraying and electric baking, the cost is relatively economic and the color is beautiful, keep for a long time.

Brake drum: brake drum is a friction couple of drum brake in drum brake system, with high and stable friction coefficient, appropriate wear resistance, heat resistance, heat dissipation and heat capacity, relatively high strength and stiffness, but will be brittle after aging.

The brake drum is an important part of drum brake, which is similar to the brake disc in disc brake. When braking, the piston applies pressure on two half-moon shoes against the inner wall of the tympanium, creating friction to stop the wheel's rotation.