Disc Brakes
The disc brake slows or stops the rotation of a wheel. A brake disc is usually made of cast iron or ceramic and is connected to the wheel. To stop the wheel, friction material in the form of brake pads (mounted in a brake caliper) is forced hydraulically against both sides of the disc. Friction causes the disc and attached wheel to slow or stop.
Disc brakes don't suffer from seizing (as drum brakes do) for several reasons, Firstly, they work by forcing a pair of pads against the outside of a spinning disc. Because, certainly on the front, they don't need to produce any hand brake effect, there is no mechanical adjustment and wear in the pads is compensated for by slightly greater piston travel.
A further benefit of discs brakes is that the friction generation process takes place in open air, so there is far better cooling of the whole operatior And to improve this even further, for hard braking applications (such as track days or motorsport), additional air can be ducted onto the brakes to cool them even more.
Discs will also usually be ventilated, with a series of vanes allowing air into the middle section of the disc, increasing the surface area that the cooling air comes into contact with and removing yet more heat for better efficiency.
