Drum brake

Drum brakes, also called block brakes, are braked by pressing the brake pads on the brake wheels. Drum brakes were an early design of the brake system. The brake drum design was used in the carriage in 1902 and was not widely used in the automotive industry until around 1920. Nowadays, the mainstream of the drum brake is the inner tension type, and its brake block (brake brake) is located inside the brake wheel. When the brake is applied, the brake block is opened outward, rubbing the inner side of the brake wheel to achieve the purpose of braking. Compared with the disc brakes, the drum brakes have much worse braking performance and heat dissipation. 

The drum brakes have poor braking force stability, and the braking force varies greatly on different road surfaces and is not easy to control. Due to poor heat dissipation, a large amount of heat is accumulated during the braking process. Brake blocks and drums are more susceptible to extremely complex deformation under the influence of high temperature, which is prone to brake degeneration and chattering, resulting in reduced braking efficiency. In addition, after using the drum brake for a period of time, it is necessary to regularly adjust the gap of the brake shoe, and even remove the entire brake drum to clean up the accumulated brake powder. 

Of course, drum brakes are not without merit, they are cheap and conform to traditional designs. During the braking process of the four-wheeled sedan, due to the inertia, the front wheel load usually accounts for 70%-80% of the total load of the car. The front wheel braking force is larger than the rear wheel, and the rear wheel plays the auxiliary braking role. In order to save costs, the manufacturer uses the brake method of the front and rear drums. However, for heavy-duty vehicles, because the speed is generally not very high, the brake shoes are also more durable than the disc brakes, so many heavy-duty vehicles still use the four-wheel drum design.