The brake drum is an important part of the automobile brake system, and its design and manufacturing quality directly affect the braking performance and safety of the automobile.

The brake drum working surface is generally finished with the bearing hole positioning after assembly with the hub. Mini cars require roundness and coaxiality tolerances of working faces ≤ 0.03mm, radial runout ≤ 0.05mm, and static unbalance ≤ 1.5N · cm.

The brake drum is a fragile gray cast iron material, similar to the iron casting of the tambourine, fixed to the tire and rotating at the same speed. When braking, the oil pressure pushes the brake shoe to contact the inner edge of the brake drum, and the friction generated by the contact rotates the tire to achieve the purpose of braking. The brake drum is not properly designed or easily deformed when heated, and the unbalanced force will cause mechanical deformation and poor contact, which will increase the pedal force and stroke. Therefore, the brake drum should have sufficient wall thickness, and the outer surface near the opening of the cast circumferential or axial reinforcement to improve strength.

The brake drum wear limit refers to the thickness of the brake drum that gradually decreases due to friction and wear during use. When the brake drum is worn to the extreme limit (for example, the limit value of the brake drum with a diameter of 180mm is φ180mm), it needs to be replaced.