Disc brakes have been around for some time now. They were first developed in the 1890s but didn't see mass production till about 1950 in the U.S. The principle is fairly simple. You have a brake caliper that houses the brake pads and caliper piston(s). When the brakes are applied, hydraulic pressure is exerted on the back of the caliper piston and the brake pads make contact with the brake rotor, thus converting the motion of the vehicle into heat. In its simplest terms, brakes turn speed into heat.
Disc brakes are commonplace on the front wheels of modern vehicles, and can also be found on the rear wheels of many other vehicles. The design of the front and rear disc brakes might differ, but in operation, they are virtually the same. The exception with rear disc brakes is that many times the parking brake is part of the rear caliper assembly. We'll get into that more in the section on rear disc brakes. For now, let’s talk about some of the common problems with disc brakes.