What does a proportioning valve do?
The proportioning valve has an important function for the brake system to maintain the comfort and safety of the car while driving during the braking process. A proportioning valve is a valve that relies on the statics to supply a reduced pressure to an output line. Proportioning valves are frequently used in cars to reduce the brake fluid pressure to the rear brakes.
When a car brakes suddenly at high speed, the car's body's inertia force will push the vehicle forward. This thrust causes the car's center of gravity to also shift towards the front.
The center of gravity's shift towards the front causes the front of the car to experience heavier friction and loads than the car's back. We can feel the symptoms more in the front engine car type. Look at the example in the image below.
If the braking pressure between the front and rear wheels is the same, then the rear wheels, which have a lighter load, tend to lock faster. It can result in the rear wheels losing traction (grip) to the road so that the rear wheels become slip.
When the slip occurs on the rear wheels and the wheels' traction on the road decreases, the car's rear body can move wildly to the right or the left. This condition makes the steering difficult to control, so it needs to be prevented to avoid accidents' potential and risk.
The Brake proportioning valve function
Therefore, to ensure the car's movement does not run wild during sudden braking at high speed, the braking force on the rear wheels must reduce than the braking pressure on the front wheels. Pay attention to the example of the ideal brake pressure graph between the front and rear wheels, as shown below.
When the rear wheel braking pressure is lower, it can prevent the rear wheels from locking up earlier than the front wheels.
Also read:You can reduce the hydraulic pressure from the master cylinder to the rear wheel cylinder by adding a proportioning valve component. The proportioning valve is generally attached to the brake lines leading to the car's rear wheels.
The proportioning valve function is to reduce the braking force on the rear wheels automatically. So it is not interfering with comfort while driving.