Drum Parking Brakes
Drum brake parking assemblies are gradually being replaced by disc brake systems. This is true because they are less costly and less complex to manufacture and assemble. The rear drum parking brake system uses a cable and some leverage to apply the parking brakes. A cable is attached to the lower portion of the brake lever and the upper portion is attached to a swivel on the secondary shoe.
The secondary shoe is the shoe facing the rear of the vehicle. In the illustration you see that the parking brake strut is the member that acts upon the primary shoe, facing the front of the vehicle. These two parts work together to apply both the secondary and the primary shoes with equal force.
As the driver engages the parking brake the cable pulls the lever forcing the secondary shoe in one direction and primary in the other. It does this by acting upon the brake strut located between the two. As you can see it is because this strut is located further down the lever arm than the swivel that it forces the primary shoe outward.
Its simple, ingenious, and becoming out dated. You will also find that many of these strut bars have star adjusters incorporated. Its important to keep these systems adjusted properly to maintain proper parking brake tension and operation.
