A brake drum is a cast iron shaped like a tambourine that is fixed to a tire and rotates at the same speed. Brake Shoes Apply oil pressure to push Brake Shoes to touch the inner edge of the Brake drum. The friction force generated by contact restrains the rotation of the tire to achieve the purpose of braking. Drum brake is composed of brake bottom plate, brake pump, brake shoe and other related connecting rod, spring, pin and brake drum. Currently only commonly used in the rear wheel. Drum brakes, which cost less and have higher absolute braking power, are more widely used in the rear wheels of small cars. But its attrition rate is higher, therefore the whole cost is higher at the same time.