How they work: When you pull the lever, it pushes a piston in a master cylinder within the lever body. This forces hydraulic fluid (mineral oil or DOT fluid) through a sealed hose down to the brake caliper.
Result: The fluid pressure pushes the caliper's pistons, which press the brake pads against the spinning rotor (disc), creating friction to slow the wheel.
Key Features:
Exceptional Modulation and Feel: They allow for very fine control over braking force with minimal effort.
Self-Adjusting: As the brake pads wear, the system automatically repositions the pads closer to the rotor.
Road Bike Integration: On bikes with drop handlebars, the hydraulic brake lever is often integrated with the gear shifter into a single unit.