Improper design of the brake drum, easy to change when heated; unbalanced force of the brake drum will also produce mechanical deformation, which will cause poor contact between the shoe and the drum, resulting in increased pedal force and stroke; when the working surface of the brake drum is too large, it will also cause self-locking and produce vibration and noise. Therefore, the brake drum should have sufficient wall thickness, and the outer surface near the opening part of the cast circumferential or axial reinforcement to improve strength. These stiffeners also play the role of heat dissipation, which can reduce the temperature of the friction surface, shorten the cooling time of the brake, and increase the energy capacity by 35% to 40%.
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.