The drum brake consists of two parts: a brake frame and an electric hydraulic pusher. When braking, the wheel cylinder piston pushes the brake shoe outward under the action of the brake fluid pressure, and the brake shoe overcomes the elastic force of the return spring. Open, press against the brake drum, and generate braking torque to brake the car. The working principle of the drum brake is to push the piston of the brake master cylinder to move when the brake pedal is stepped on, and then generate pressure in the oil, make it open outward and press against the brake drum to generate braking torque. The components of drum brakes include brake wheel cylinders, brake shoes, brake drums, friction linings, return springs, etc. Drum brakes are in the car field. It has been gradually withdrawn and is mainly used to brake rear wheels and parking brakes with relatively small loads. The working principle of drum brakes also includes the effect of self-increasing or self-decreasing torque. The friction of the leading shoe is from 2 to 2.5 times