Parking Brake Mechanisms
The parking brake system is a secondary braking system used to hold a parked car in position. They are applied independently of the service brakes. Since there is no inertia to overcome, less braking power is required to hold the vehicle stationary and less force is required to apply. The application of only two of the four brake assemblies are required to hold the vehicle.
There are three styles of rear parking brake systems. Two types use the service brake and the other is an exclusive parking brake design. The service type parking brake uses part of the ordinary service brake mechanism and operates the shoe or piston mechanically.
The parking brake lever is located near the driver’s seat. Pulling the parking brake lever by hand or pressing the pedal with the foot, operates the brake via a cable connected to the parking brake lever of the brake assembly.
There are a number of different types of parking brake levers, as shown below. Application depends upon the design of the driver’s seat and the desired operating effort. The parking brake lever is provided with a ratchet locking mechanism to maintain the lever at the position to which it was set, until released. Some parking levers have an adjusting screw near the brake lever so the amount of brake lever travel can be easily adjusted. Travel is determined by the number of clicks of the ratchet mechanism found in the Repair Manual.
Parking Brake Linkage:
The parking brake cable transmits the lever movement through a typical series of components, as shown below, to the brake drum sub-assembly. The Intermediate Lever multiplies the operating force to the Equalizer. The Equalizer divides the lever operating force to brake assemblies at both wheels. The two major parts may vary in design however, their function remains the same.
Drum Parking Brake:
On all models using drum brakes on the rear, the cable pulls the parking brake lever. The lever is attached to the secondary shoe at the top and transfers the lever action to the primary shoe through the shoe strut. When released, the brake shoe springs return the shoes to their retracted position.
Disc Parking Brakes:
There are two types of rear wheel parking brake systems for disc brakes. The first uses the brake caliper assembly to mechanically apply pressure to the disc. The second type is an exclusive drum brake assembly that applies pressure to an inside drum, which is an integral part of the disc rotor.
Caliper Parking Brake:
The parking brake is built into the caliper housing and is provided with an automatic adjusting mechanism to compensate for piston movement as the brake pads wear.