If you have decided that you want disc brakes, the next step is
determining whether you want mechanical or hydraulic mountain bike disc
brakes. There is a lot of controversy on which type is better. There are
very good brands of both types.
Mechanical Disc Brakes
With mechanical mountain bike disc brakes, a tensioned steel cable activates pistons that cause the brake pads to compress against the rotor when the brake lever is pulled.
All mountain bike brakes operate by the same general principal. A lever
is pulled on the handlebar which causes a cable or fluid to compress brake pads
against either the wheel rim or a rotor to slow down or stop the wheel.
The left brake lever always operates the front wheel brake and the
right lever operates the rear wheel. 1. Rim Brakes
With rim brakes, the brake lever is pulled and brake pads are compressed against the rim of the wheel.
There are several different types of rim brakes, including v-brakes,
u-brakes, cantilever brakes, or direct pull brakes, but you mostly see