I. Disc Brake History and Overview
A. Basic Brake Design
Disc brake systems generate braking force by clamping brake pads onto a rotor that is mounted to the hub. The high mechanical advantage of hydraulic and mechanical disc brakes allows a small lever input force at the handlebar to be converted into a large clamp force at the wheel. This large clamp force pinches the rotor with friction material pads and generates brake power.
Hydraulic disc brakes utilize a master cylinder mounted on the handlebar to produce the input force at the lever and push brake fluid to a hydraulic caliper at the wheel which generates the clamp force.
Mechanical disc brakes utilize normal bicycle cable brake levers to pull a cable and actuate a mechanical caliper. Mechanical Calipers have internal components that can convert the cable force into a clamp force.
Brake Power is generated when the caliper brake pads clamp the rotor. As a general rule, three factors will determine how much brake force is generated: