The brake drum is not designed properly and is changeable when it is heated. Brake drum force imbalance, will also produce mechanical deformation, so that the hoof and drum contact is not good, resulting in pedal force and stroke increase; Brake drum working surface roundness is too large, will cause self-locking and vibration, noise. So the brake drum should have enough wall thickness, and the outer surface near the opening casting out of the circumferential or axial reinforcement to improve the strength. These reinforcing bars also have the function of heat dissipation, which can reduce the friction surface temperature, shorten the brake cooling time, and increase the energy capacity by 35%~40%.

Brake drum working face is generally machined with bearing hole positioning after assembling with wheel hub. The working surface tolerance of the mini car is required to be ≤0.03mm for roundness and coaxiality, ≤0.05mm for radial runout, and ≤ 1.5n ·cm for static unbalance.