How to Make Your Car Last Forever: Avoid Expensive Repairs, Improve Fuel Economy, Understand Your Warranty, Save Money

The proportioning valve is a metering valve designed to differentiate hydraulic fluid pressure between the
front and rear brakes. Typically, front brakes need more stopping power than rear brakes because there’s a lot
more weight in the front of the vehicle with the engine, transmission, axles, and so on than in the back.
Therefore there has to be more braking power in the front to stop forward motion than in the rear.