Brake Proportioning/Combination Valve: Description and Operation

PROPORTIONING VALVES
The proportioning valves limit the outlet pressure to the rear brakes on the non-antilock braking system (ABS) after a predetermined master cylinder pressure has been reached. This is used when less rear apply force is needed to obtain optimum braking and is usually found on disc/drum brake configurations. On vehicles equipped with ABS, refer to Antilock Brake System.