Metering valve

[1] A valve positioned in the hydraulic line to the front brakes, on some cars with front disc and rear drum brakes. It prevents the disc brakes from applying until after the rear brake linings contact the drum. The metering valve closes off pressure to the front disc brakes until a specified pressure level is generated in the master cylinder. This allows pressure in the rear brake circuit to overcome return spring force and an gap before the hydraulic pressure is admitted to the front disc brakes
[2] A hydraulic control valve placed in the circuit to the front brakes, designed to restrict pressure to the front brake calipers until the rear brake shoes overcome the tension of the retracting spring