Hydraulic brakes are bicycle brakes that use fluid pressure to stop the bicycle. The bicycle's pedals are connected to a piston in the bicycle's frame, which pressurizes fluid in a chamber in the bicycle's frame. The fluid then flows through a hose to the bicycle's brakes, where it pressurizes a second chamber. This pressurized chamber forces a pad against the bicycle's rim, causing the bicycle to slow down or stop. Hydraulic brakes are more effective than mechanical brakes, and they require less effort to operate. As a result, they are often used on mountain bikes and other bicycles that are subject to heavy braking.