Drum brake is composed of brake bottom plate, brake sub pump, brake shoe and other related connecting rod, spring, pin and brake drum. It is the use of hydraulic device in the brake drum in the brake pad to push outwards, so that the brake pad and with the wheel rotation of the brake drum surface friction, and the effect of braking.

Drum brakes have been used on automobiles for nearly a century, but due to their reliability and powerful braking force, drum brakes are still used on many models today (mostly on the rear wheels).

The drum brake has a cast iron shaped like a tambourine, called a drum, which is fixed to the tyre and turns at the same speed. The inner surface of the drum of drum brakes is the position where the braking torque is generated by the brake device. Under the condition of obtaining the same braking torque, the diameter of the brake drum of the drum brake device can be much smaller than that of the disc brake. Therefore, in order to obtain powerful braking force, a large vehicle with heavy load can only be equipped with drum brakes in the limited space of the wheel rim.

To put it simply, drum brake is a brake device that uses the stationary brake pads in the brake drum to rub the drum that rotates with the wheel to produce friction force to reduce the speed of the wheel.

When the brake pedal is pressed down, the force applied by the foot will cause the piston in the main brake pump to push the brake oil forward and create pressure in the oil path. The pressure is transmitted through the brake oil to the piston of the brake sub-pump of each wheel, and the piston of the brake sub-pump pushes the brake pad outward, so that the brake pad frictions with the inner surface of the brake drum, and generates enough friction to reduce the speed of the wheel to achieve the purpose of braking.