wheel cylinder function Page 790

In a drum-brake setup, the wheel cylinder is the small hydraulic enforcer that turns your pedal push into shoe-splaying force.

Press the brake and fluid pressure drives two pistons outward, shoving the shoes against the drum to make friction and, ideally, stop you before the servo chook shop.

Inside are pistons, seals and dust boots doing the hard yards, while return springs in the drum haul the shoes back when you lift off.

Tell-tale drama includes leaks at the backing plate, a spongy pedal, the car pulling to one side, or mysteriously low brake fluid.

If it’s leaking or seized, replace or rebuild them in axle pairs and bleed the system properly—brakes aren’t the place for guesswork.