Brake pressure proportioning valve (Brakes)

Brake pressure proportioning valve

The fluid lines for both hydraulic circuits are connected to the valve, but the circuit for the front brakes uses the valve purely for distribution.

Pressure to the rear brakes passes through a piston sleeve, past a poppet valve and out to the rear brakes. The same pressure is also felt on the top of the piston, forcing the piston against spring pressure, towards the valve centre until the piston sleeve contacts the poppet valve and forms a seal. Input pressure is now balanced with output pressure. As further input pressure is applied from the master cylinder, it overcomes output pressure being felt on the piston and forces the piston outwards slightly away from the poppet valve allowing pressure past the poppet valve until output pressure is again balanced with input pressure.