A brake cylinder is used in conjunction with a brake drum and is a type of brake system that pre-dates the caliper and rotor setup.
A brake cylinder is part of the hydraulic system; pressing the brake pedal forces the integrated brake cylinder pistons outward, forcing the brake shoes against the rotating brake drum.
Where’s a Brake Cylinder Located?
While brake cylinder and drum brakes (we call them drum brakes) are old technology, they are still used today. That said, they are much less common today; it’s more usual for passenger vehicles and light trucks to have calipers and rotors on all four wheels.
Lower speced models, however, may have drum brakes, but they will only ever be fitted to the rear wheels, never the front. Commercial vehicles are different; heavy trucks typically employ drum brakes on all four wheels.
Common Brake Cylinder Problems
The single most common brake cylinder issue is fluid leaks. The brake cylinder employs two pistons that slide forward to apply the brake shoes and retract afterward. The pistons are pushed from behind by the pressurized brake fluid; however, cylinder seals are used to prevent fluid from leaking out.
Constant piston movement eventually wears out the seals and causes the fluid to leak and typically onto the brake shoes contaminating them.
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John Cunningham is an Automotive Technician and writer on Rustyautos.com. He’s been a mechanic for over twenty-five years and has worked for GM, Volvo, Volkswagen, Land Rover, and Jaguar dealerships.
John uses his know-how and experience to write fluff-free articles that help fellow gearheads with all aspects of vehicle ownership, including maintenance, repair, and troubleshooting.