Brake Master Cylinder Notes

Brake Master Cylinder

Function

  • Converts force from foot/fingers into hydraulic pressure.
  • Almost always a tandem brake master cylinder.

Components of a Compensating Port Master Cylinder

  • Reservoir tank: Contains brake fluid.
  • Cylinder: Houses the internal components.
  • Rubber piston cups: Create brake circuits.
    • A tandem master cylinder has two brake circuits.
  • Compensating ports: Located in the top part of the cylinder.
  • Outlet ports: Located on the side of the cylinder for connection to the brakes.

Operation of a Compensating Port Master Cylinder

  1. Push rod pushes the first rubber piston cup over the compensating port.
  2. Pressure builds in the first brake circuit.
  3. The second rubber piston cup is moved over the second compensating port.
  4. Pressure builds in the second brake circuit.

Split Brake Systems

  • Mandatory in many countries for safety.
  • If one brake circuit fails, the other still works.
Types of Split Brake Systems
  • Front-rear split:
    • First circuit: front brakes
    • Second circuit: rear brakes
  • Diagonal split:
    • One circuit: one front and one rear brake (diagonally opposed).

Portless Master Cylinders

  • Used with ABS (Anti-lock Braking System).
  • No compensating port.
  • Brake fluid enters through the breather port.
  • Breather port provides fluid when the intake valve is open.
  • Pressure builds when the valve is closed, applying the brakes.

Additional Components

  • Hydraulic lines: Carry brake fluid to the front and rear brakes.

Hydraulic System in Action

  • Master cylinder pressurizes the entire system.
  • Brake fluid is forced through the hydraulic lines.
  • Reservoir ensures sufficient brake fluid to prevent air entry.

Brake Pedal Positions

  • Hold: Both valves are closed.
  • Applied: Atmospheric valve open, vacuum valve closed.
    • Atmosphere goes in.
  • Release (Suspended): Vacuum open, atmospheric closed.