Disc brakes are used since the early 1970s. A disc brake operates by squeezing brake pads on both sides of a rotor or disc that is attached to the wheel.Due to the friction between the road surface and the tires, the vehicle stops.

Typical disc brake assembly

Disc brakes use a piston to squeeze friction material (pads) on both sides of a rotating disc (rotor)

The rotor is attached to and stops the wheel

Except for this disadvantage, disc brakes have the following advantages over drum brakes:

•  More fade resistant. The disc and pads are usually mounted where air can cool the parts quickly. In fact, over 80 percent of the rotor is exposed to the air. Also, as the rotor becomes hotter, the rotor expands toward the friction pads, not away from the shoes as happens with drum brakes.
•  Even, straight stops. The friction of disc brakes is directly proportional to the pressure applied. Drum brakes, however, tend to give uneven braking because the self-energising actions tend to be uneven side to side.
•  Wet stopping is possible. The water simply runs off the vertical rotor surface and the pads constantly rub against the rotor surface, effectively preventing water build-up and wet brake fade.
•  Fewer service parts. Because of fewer actual parts, most disc brake service is often easier than similar drum brake service.