Parking brakes can be incorporated into brake rotor systems, but the majority of parking brakes utilize the drum brake system. A damaged park brake cable may not allow the brake shoes to return to their original position, causing brake wear.
When the drum brakes are applied by the driver's foot on the brake pedal, hydraulic fluid forces the wheel cylinder to expand and apply the brakes. The parking brake is almost always operated by a cable, not by brake fluid pressure. When the parking brake is applied, a cable pulls a lever which forces the brake shoes to spread apart, pushing them against the inside of the brake drum to stop the vehicle from moving.
The parking brake also operates the auto-adjuster inside the brake drum. The auto-adjuster is the bar that goes between the two brake shoes. The star-shaped wheel or gear is attached to a threaded bolt. Each time the parking brake is applied and released, an arm tries to turn that star gear to ensure that the brake shoes remain close to the drum, but not touching when the brakes are released.
A common problem experienced with the parking brake system is when the cable that operates the parking brake does not move freely inside its casing. This can cause either the cable not to allow the brake to be applied, or more frequently it may allow the brakes to be applied but not move back freely to allow the brake to release -- causing the brake shoes to overheat and wear prematurely.
Some newer vehicles with brake rotors on the rear wheels incorporate an electromechanical parking brake or EPB. Unlike drum brakes, EPB's apply the rear brakes to hold the vehicle in place when it is parked. EPB systems include all the normal parts of a brake rotor system, such as brake pads, calipers and rotors, but also include an electric motor connected to the brake caliper.
Vehicles with an EPB system use an electrical switch to apply the park brake instead of a handbrake lever or park break pedal, and the brakes are usually applied automatically when the vehicle is turned off.
When the brake pedal is pressed, the piston on the caliper moves outwards as a result of the hydraulic fluid being pressurized, but when the EPB is applied, the electric motor connected to the brake caliper spins a threaded shaft that pushes against the back of the caliper piston in order to hold the brake pads against the rotor.
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Function: A steel cable that connects the parking brake lever to the brake system in order to keep the vehicle from moving.
Signs of Wear: Inability to secure parking brake, looseness in brake lever, rear wheel lockup, vehicle rolls after parking brake is secured.
Professional Auto Care
Professional Auto Care is an award-winning family owned and operated auto repair shop located in southwest Houston. It has been run by the same family, the Serratos Family, for nearly 35 years. Professional Auto Care services Domestic, Asian as well as select European vehicles. We are known for our professionalism, transparency and quality of work. Since our humble beginning in 1983, we always strove to provide the best, most reliable service in Houston with a hint of the personal touch. The founders, Everardo and Claudia Serratos, are still involved with the daily operations of the car maintenance and auto repair shop.