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An Overview Of Bias Proportioning Valves

Updated on March 30, 2012

What Are Bias Proportioning Valves?

Bias proportioning valves are basically a component in an automobile’s brake system. These help in controlling how much brake pressure is applied to the axles and also when it has to be applied.

They are placed between the master cylinder and the other components of the brake system. They ensure that the system works efficiently in all conditions which are necessary for safety and reliability.

Proportioning valves have become extremely popular over the years and are today, one of the most highly demanded performance upgrades. Vehicles designed specifically for performance purposes make use of these valves because the brake system is of key importance for these vehicles.

Common Valve Types

There are three basic types of bias proportioning valves available in the market these days. They are known as:

Master cylinder mounted
These valves are mounted on the master cylinder as their name suggests. However, they are screwed into fluid ports. These are placed between the cylinder and the brake lines.

Load sensing
These are attached to the rear end of the vehicle’s frame. A lever is used to mount these valves on to the suspension.

Combination valve mounted
These bias valves are part of the combination valves, the differential switch and metering valves. They are usually mounted on the frame just below the master cylinder itself.

Schematic Of An Adjustable Valve

Benefits of Using Brake Proportioning

There are several benefits of installing the bias proportioning valves into an automobile. The biggest advantage is that they help in reducing pressure on the brakes which helps in controlling the bias between the front and rear brakes.

The pressure on the rear brakes is reduced when the system pressure is high because of rapid deceleration. This is therefore, a very useful component because it prevents the rear brakes from locking up.

This is why these types of valves are usually recommended for lightweight vehicles like pickup trucks. Because their rear ends are typically lighter than their front ends, chances of brake lock-ups increase which is why the bias proportioning valves are important for these trucks.


A major drawback associated with using these types of valves to change brake bias is the fact that most vehicles today are being manufactured with ABS brakes, traction controls and other electronic controls. This is why these vehicles do not make use of the proportioning valves. The function of valves is handled by the electronic system itself which drastically improves efficiency and performance.

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Ford Specific Valves

There are some proportioning valves available in the market today, which have been designed specifically for Ford automobiles. This has been done in order to ensure that the best suited proportioning valves are placed into Ford models which can work efficiently with their brake systems.

It has been seen over the years that specifically designed bias proportioning valves have helped in enhancing the vehicle’s performance drastically. This is because they have been developed to perform as per the system’s requirements.

Do You Use A Brake Bias valve In Your Car?

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