How Hydraulic Braking Systems Work

Hydraulic braking systems are powerful, reliable systems relied on in automobiles and other vehicles. These systems generally involve a master cylinder, hydraulic fluid, hydraulic lines and one or more "slave" cylinders, which actuate each individual brake.

Theory

  • An automotive hydraulic braking system translates the mechanical motion of a driver's foot on the brake pedal into hydraulic pressure, which is transmitted to individual brakes, where it is turned back into mechanical motion. The system requires a fluid, metal or rubber brake lines, smaller hydraulic "slave" cylinders at each brake and the brake itself. Each automobile has four.

Master Cylinder

  • The master cylinder takes the mechanical motion from the brake pedal and converts it into hydraulic pressure. The master cylinder is basically a piston within a cylinder, filled with fluid. Modern systems have power added to them by the car and for safety also feature two separate systems, either of which will stop the vehicle. The pressure generated is distributed out to the individual brakes.

Brake Lines and Slave Cylinders

  • Individual brake lines radiate out to the brakes from the master cylinder. These brake lines are generally made of high-quality steel, resistant to corrosion and built to withstand high pressures. In cars, the last foot or two of the brake line to the wheel brake will usually be high-grade rubber, as the lines needs to move with the wheels' side-to-side and up-and-down motions. The high-pressure fluid entering a wheel slave cylinder pushes a pad or disc against a machined metal surface, and the generated friction slows the vehicle.