Shimano XTR M975 Disc Brake Caliper

About Disc Brakes

Bicycle disc brakes consist of a metal disc attached to the wheel hub that rotates with the wheel. Brake calipers are attached to the frame or fork along with pads that squeeze together on the disc. The way it is attached to the bike will be either by IS (International Standard) which has two holes facing the disc or Post Mount, which has threads going into the fork. Disc brakes have been successfully used on motorbikes for decades, and are the principal choice there. The primary benefit of disc brakes is that they perform equally well in all conditions including water, mud and snow. This is due to their position closer to the hub and away from the ground and possible contaminants like water, which can coat and freeze on the rim in colder temperatures. The pads are usually made from metal sinters or an organic compound instead of rubber. Water acts as a lubricant to rubber but not metal, therefore disc brakes maintain their stopping power in wet conditions. They also avoid the problem that rim brakes have of wearing out the wheel rims, especially in muddy conditions, as well as the requirement that the rim be straight. Disc brakes offer improved modulation of braking power and generally require less finger effort to achieve the same braking power. The advantages of discs make them well-suited to steep, extended downhills through wet and muddy off-road terrain, common in freeride bicycle riding.