Brake proportioning valves are valves that rely on the static exertion to reduce pressure to a brake line. A simple example is where spring load reduces force so that the output pressure is also reduced. Brake proportioning valves are used in cars to reduce the brake fluid pressure to the brake lines.
Since the proportioning valve are designed to decrease the pressure sent to the rear brakes, the most common symptom of the brake proportioning valve going bad is the rear wheels locking up when the brakes are applied. The wheels will also lock up more easily on wet surfaces. The rear brakes will likely feel touchy when applied even softly.
The last thing you need or want is for your rear brakes to lock up when you have to come to a quick stop. Whether you need a brake hold off valve for a 1970 Pontiac GTO, a brake 3-port metering valve for a classic E Body, or a disc brake proportioning valve for a 69 Mopar B Body we have you covered at First Place.