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How Dual Master Cylinders Work

by Jay Motes

A master cylinder is the device in a power brake-equipped vehicle that converts the pressure the driver places onto the brake pedal into hydraulic pressure. Dual master cylinders are used on most vehicles, as they have advantages over single master cylinders.


Dual master cylinders are typically a single unit that is divided inside. The master cylinder has a single brake fluid reservoir that has an interior partition as well as a single piston that is segmented to push fluid into two different brake lines.

Different Types of Brakes

Most vehicle use disc brakes on the front wheels and drum brakes on the rear. The use of dual master cylinders allows for different pressures and volumes to be placed into the brake lines to operate each type of brake system.


Dual master cylinders make power brakes less prone to failure. Each chamber of the master cylinder operates the brakes to one set of wheels. If the brake line going to one set of wheels is broken or the brake fluid is lost through other means, the other set of brakes will still work properly. In a single master cylinder system, a broken brake line would cause the power brake system to fail entirely.

About the Author

Jay Motes is a writer who sold his first article in 1998. Motes has written for numerous print and online publications including "The Dollar Stretcher" and "WV Sportsman." He holds a Bachelor of Arts with a double major in history and political science form Fairmont State College in Fairmont, W.V.

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Photo Credits

  • disque de frein image by Christophe Fouquin from