Disc brake device (Honda Accord 3)

Instead of traditional "expanding" brakes that act in opposite directions on a round drum, disc brake systems use discs with brake shoes mounted on both sides. The obvious similarity is to the hand brake on a bicycle. The shoes squeeze the rim of the bicycle wheel, slowing it down. Automobile disc brakes use the same principle, but the braking force is applied to a separate disc rather than the wheel.

The disc, or rotor, is a single unit mounted directly inside the wheel. Discs are either solid or ventilated. Ventilated discs have ribs around the circumference between the two braking surfaces to provide air access, which cools them and makes them less susceptible to thermal destruction and aging. Brake discs are slightly susceptible to the effects of dirt and water, since all sediment is thrown off by the centrifugal action of the rotor, or cleaned by the pads. Also, the equal pressing action of the two brake pads ensures an even, confident stop, while uneven pressure of the pads on the left and right wheels can cause unwanted traction when braking. All disc brakes are self-adjusting.

There are three main types of disc brakes. Fixed caliper design two pistons are used, mounted on either side of the rotor (on each side of the caliper). The caliper is rigidly mounted and does not move. This braking system is very effective, but the size of the caliper and its mounts increases the weight and size of the car.

Sliding and floating designs are very similar. In both types, one brake pad contacts the rotor under hydraulic force. The caliper, which is not rigidly fixed in position, moves slightly and ensures that the other pad contacts the rotor. There are different ways of mounting floating calipers. Some pivot around the base or top, others slide along mounting bolts. Various causes of uneven brake wear can be caused by dirt or binding at the sliding or pivoting points.