Typical Brake System

     There are two common types of brake assemblies used on modern automobiles：discbrakes and drum brakes. Disc brakes are frequently used on the two front wheels of avehicle. Drum brakes are often used on the rear wheels. However，disc or drum brakesmay be used on all four wheels.

    A disc brake assembly includes：

    Caliper - assembly that holds the cylinder, piston, and brake pads

    Caliper cylinder - machined hole in the caliper, in which piston fits

    Brake pads - friction members pushed against the rotor by the action of themaster cylinder, caliper cylinder and piston

    Rotor - metal disc that uses friction from the brake pads to stop or slow wheel rotation

    The disc brake is a lot like the brakes on abicycle. Bicycle brakes have a caliper,which squeezes the brake pads against the wheel. In a disc brake, the brake pads squeezethe rotor instead of the wheel，and the force is transmitted hydraulically instead of througha cable. Friction between the pads and the disc slows the disc down.

    A drum brake is a brake in which the friction is caused by a set of shoes or pads thatpress against a rotating drum-shaped part called a brake drum. Like the disc brake，thedrum brake has two brake shoes and a piston. But the drum brake also has an adjustermechanism，an尹ergency brake mechanism and lots of springs. Drum brakes work on thesame principle as disc brakes：Shoes press against a spinning surface. In this system，thatsurface is called a drum.

    A drum brake assembly includes：

    Wheel cylinder assembly - houses a hydraulic piston that is forced outward byfluid pressure

    Brake shoes - friction units that are pushed against the rotating brake drum bythe action of the wheel cylinder assembly

    Brake drum - rubs against the brake shoes to stop or slow wheel rotation