There are brake disc brake drums and air brakes, some of the older cars use front drum. Morden cars use disc brakes. Brake disc heat better, in the high-speed braking state, not prone to heat decline, so its high-speed braking effect. However, in low-speed cold brake, the braking effect is not as good as the brake drum. Brake disc is expensive than the brake drum. So now many high-class cars with full brake disc, and ordinary cars with front disc drum, and relatively low speed, and need a large braking force truck, bus, still using drum brake.
Drum brake is sealed, shaped like a drum, there are many in the country called brake pot. It is spinning when driving. Inside the drum brake there are two curved or semi-circular brake shoes. Brake brake when the two brake shoes in the wheel cylinder under the effect of Zhang, prop up the brake shoe friction brake drum wall to play the role of deceleration or parking.
Brake disc material is the use of China's gray cast iron 250 standards, referred to as HT250, equivalent to the same as the United States G3000 standards. The chemical composition of the three major elements of the requirements are: C: 3.1 ∽ 3.4 Si: 1.9 ∽ 2.3 Mn: 0.6 ∽ 0.9. Mechanical requirements: Tensile strength> = 206MPa, flexural strength> = 1000MPa, deflection> = 5.1mm, hardness requirements: between 187∽241HBS