How Disc Brakes Work

On a disc brake, the fluid from the master cylinder is forced into a caliper where it presses against a piston. The piston, in turn, squeezes two brake pads against the disc (rotor) which is attached to the wheel, forcing it to slow down or stop. This process is similar to a bicycle brake where two rubber pads rub against the wheel rim to create stopping friction.

The main components of a disc brake system are the Calipers, Brake Pads, and Rotors (or discs).

Calipers

Calipers must be rebuilt or replaced if they show signs of leaking brake fluid. There are two main types of caliper: floating and fixed. Single Piston Floating Calipers are the most popular and also least costly to manufacture and service. A floating caliper "floats" or moves in a track so that it can center itself over the rotor. As you apply brake pressure, the brake fluid pushes in two directions. It forces the piston against the inner pad, which in turn pushes against the rotor. It also pushes the caliper in the opposite direction against the outer pad, pressing it against the other side of the rotor. On some vehicles there two pistons mounted on the same side.

Brake Pads

There are two brake pads on each caliper. They are constructed of a metal "shoe" with the lining riveted or bonded to it. The pads are mounted in the caliper, one on each side of the rotor. These brake pads wear out with use, and must be replaced periodically. Therefore, they should be routinely checked for wear. If the lining wears down to the metal brake shoe, then the shoe will rub directly against the rotor which cause a loss of braking efficiency and quickly will cause damage to the rotors and the shoes.

Most brake pads now come with a "brake warning sensor" that will emit a squealing noise when the pads are worn to a point that they should be changed. This noise will usually be heard when your foot is OFF the brake and will disappear when you stop ON the brake. When you hear this noise, you will want to make an appointment to have your brake pads replaced.

Brake Rotor

The disc rotor is made of iron and highly machined surfaces where the brake pads contact it. The rotor will also wear over time, usually in the form of ridges and grooves where the brake pads rub against it. This wear pattern will exactly match the wear pattern of the pads as they seat themselves on the rotor. When the pads are replaced, the rotors must be machined smooth to allow the new pads to have an even contact surface.

A minimum thickness measurement is stamped on every rotor, and once a rotor is cut below the minimum, it won't be able to handle the high heat that brakes normally generate. When this happens, the rotors will need to be replaced.

If you have reason to believe that your brakes need attention, our brake experts will be happy to take a look for you.