The brake drum is a kind of cast iron similar to tambourine, which is fixed and rotated at the same speed with the tire. When braking, the brake shoe (Brake Shoes) is pushed by oil pressure to contact the inner edge of the brake drum, and the friction force produced by the contact is used to restrain the rotation of the tire to achieve the purpose of braking. Drum brake consists of brake base plate, brake sub-pump, brake shoe and other related connecting rods, springs, pins, brake drum. At present, it is commonly used only in rear wheels. Drum brakes are less expensive and have higher absolute braking power. They are widely used in rear wheels of small cars. But the wear rate is high, so the overall cost is high.