Brake Proportioning/Combination Valve: Description and Operation
PROPORTIONING VALVEDESCRIPTION
NOTE: Only vehicles without antilock brakes have proportioning valves. Vehicles with antilock brakes have Electronic Variable Brake Proportioning (EVBP) that is built into the integrated control unit.
On the non-antilock master cylinder, two screw-in proportioning valves are screwed directly into the rear brake outlet ports (Fig. 117). The chassis brake tubes leading to the rear brakes attach to the outlets of the proportioning valves. One proportioning valve controls each rear brake.
OPERATION
Proportioning valves balance front to rear braking by controlling the brake fluid hydraulic pressure to the rear brakes above a preset level (split point). Under light pedal application, the proportioning valve allows normal fluid flow to the rear brakes. Under higher pedal effort, the valve reduces fluid pressure to the rear brakes. This helps prevent rear wheel skid tendencies.