Drum brake can be divided into potential assistant and potential reducing shoe, double potential assistant shoe and two-way automatic force increasing type. A double piston brake wheel cylinder is installed for the potential assisted and potential reduced shoe brakes. No matter what direction the brake drum is turning, there is only one potential assisted shoe. It has simple structure and reliable use. When the car is braked forward or backward, the brake effect remains unchanged. It is mainly used for the rear wheels of the car. The double potential assisted shoe brake is mostly used in front wheels of cars. Generally, it is equipped with two single piston brake wheel cylinders, and the two brake shoes are movably connected by connecting rods. When the car moves forward, both brake shoes are potential shoes, but when reversing, they become potential reducing shoes, and the braking effect is significantly reduced. The two brake shoes of the two-way automatic force increasing brake are connected by bars and share one support. The double piston brake wheel cylinder pushes the brake shoes away from both sides. No matter which direction the brake drum rotates, the automatic force increasing effect can be obtained. However, the braking is not smooth and the performance of the friction material is required to be high.

Drum brake can increase force automatically, and the contact area between brake drum and brake shoe is large. The brake effect is better at low speed. However, because the brake shoe and drum are in closed state and have poor heat dissipation, they are not suitable for high-speed and long-term continuous brake. Moreover, the brake effect will be significantly reduced after the brake shoe friction plate is immersed in water.