Where is the brake proportioning valve

Then, ABS hardware intervenes and modifies brake pressure when necessary. This is all based on wheel slip, unlike proportioning valves, which are based on brake line pressure.

If your valve is not operating optimally, it might be time to tweak or replace it. You might be tempted to try to accomplish this on your own, but making changes to the brake bias should only be done by those with proper training, tools, and devices. Choosing the right slope and knee point is a tedious and detail-oriented process.

If you have more questions about proportioning valves, you should watch our informational video. Enter your email address and we'll email you a digital version of this coupon that you can present on your mobile device at your Sun Devil Auto Shop. Skip to content. Find a Location Locations. Make An Appointment Appointments. Function and Purpose of the Proportioning Valve The proportioning valve typically connects the master cylinder to the rest of the braking system, but sometimes it is independent of the cylinder.

Advantages for Your Car You benefit by having a brake proportioning valve in your brake system because it helps you control brake balance. Three Different Types of Brake Proportioning Valves With all of this being said, it is important for you to know that there are three kinds of proportioning valves used in cars. They are: Master Cylinder-Mounted: These valves are located directly on the cylinder and attached to fluid ports located between the cylinder and brake lines.

Load Sensing: These valves are located directly on the frame at the rear end of the vehicle, with a lever attaching it to the suspension system. Combination Valve-Mounted: These valves are part of a larger valve with the metering valve and pressure differential switch. This type of valve is usually mounted to the frame or inner fender below the master cylinder.

Signs of a Failing Proportioning Valve Just like any other part of your car, the proportioning valve may eventually fail. As a refresher from our bias article, we will bring forward again the lists of modifications which can influence front-to-rear bias. We could start this section by clearly stating that you should not modify your proportioning valve.

But, what fun would that be? In all seriousness, making changes to the proportioning valve to effect brake bias should be left to those with the proper tools and measurement devices, but if you have tweaked your vehicle beyond recognition, this may be your only solution to restore a sense of proper bias to your braking system. If you have the deeply-rooted need to install your own adjustable proportioning valve, be advised that they should NEVER be installed if the factory unit is still in place.

Proportioning valves in series with one another can do nasty, unpredictable things! If you have the deeply-rooted need to install your own adjustable proportioning valve, be advised that they should NEVER be installed in-line to the front brakes.

In all cases, the basic brake system balance needs to be close to optimized to start with. This is the only way that a proportioning valve can be effectively utilized. You should never assume that simply adding a proportioning valve will address all rear-bias conditions, as even the best proportioning valves must be well-matched to the target vehicle. Selecting the correct adjustable proportioning valve for your vehicle entails not only selecting the proper point at which slope limiting begins the kneepoint , but also selecting the proper rate at which rear brake line pressure builds after that point the slope.

Nearly every adjustable proportioning valve on the market today has an adjustable knee point the point at which the rear brake line pressure begins to be controlled , but a fixed slope the rate at which it builds beyond the knee point. While one parameter is adjustable, both are critical to system performance. Note that in Figure E the two curves have the same knee point, but the slopes vary greatly.

So how does one select the right kneepoint and slope? Of course, you could trial-and-error your way into a solution that you believe to be appropriate, but without testing under all conditions of loading, speed, and road conditions there might be one operating condition just waiting to bite you. As a small sidebar to the mechanical proportioning valve discussed here, there is a movement afoot to replace the proportioning valve function with the hardware performing the ABS function.

While this is not yet the norm, most high-end performance cars already have this feature as standard equipment and one can predict with reasonable certainty that the trend will continue. Then, given preset thresholds and parameters, the ABS hardware can intervene and modify the brake pressure going to the rear wheels automatically.

Because DRP and EBD are based on actual wheel slip and not on brake line pressure, this type of rear proportioning is more flexible and adaptable to modifications one might make to their vehicle.

It is also less expensive, as the OEM can now remove the mechanical proportioning valve from the vehicle and replace its function with other hardware already on board. Naturally, the OEM does not want owners fiddling with their front-to-rear proportioning, and as a result there is no way for the enthusiast to reprogram DRP or EBD to suit their desires.

In summary, there is more to the proportioning valve than meets the eye. You should make every attempt to carefully plan and select your brake modifications so that you are able to retain and reap the benefits of the stock proportioning valve. If for other reasons you are forced to scrap the stock and replace it with an aftermarket unit, be advised that selection and adjustment are not for the uninitiated. While there is more than one way to achieve optimum balance at the point of maximum deceleration, without the right amount of know-how you might be making compromises under partial braking conditions that were not present with the factory hardware.

Again, remember that simply adding or replacing a proportioning valve may not be enough to remedy basket-case bias scenarios. Proper planning and up-front design should ensure that the base vehicle bias is appropriate from the start, enabling the proportioning valve to be used properly as a fine-tuning device.

The store will not work correctly in the case when cookies are disabled. Search by car. If the pressure on one side is greater, the valve inside can actually move and therefore block off any fluid from going to that side of the brake system.

The valve includes three critical components. The proportion valve works in a panic situation to hold off rear brake pressure and prevent rear brake lock-up. Topics: How To Series. Copyright Master Power Brakes. All Rights Reserved. Sign In My Cart. Tech Talk with Master Power Brakes. How Do Combination Valves Work?

What Does a Combination Valve Do? Brake Pressure Differential Switch and Valve In the center of the combination valve labeled as B in the image below is a single wire connector that works in conjunction with a slide in the center of the valve.

Proportioning Valve The proportioning valve part of the combination valve is located in the rear brake portion of the valve. Recent Posts.