A brake proportioning valve is a device that is attached to the side of the master cylinder. It limits how much brake pressure that can be applied to the front or rear wheels during moderate brake applications to prevent premature wheel locking and to provide a reliable brake system operation. A malfunctioning proportional valve will distribute equal pressure amount to the car wheels, causing the rear wheels to lock up prematurely before coming to a complete stop. Auto Parts Network provides the parts needed in keeping your vehicle in good driving and braking performance.
Brake Proportioning Valve 
