Final answer:
The primary and secondary shoes on an adjuster assembly refer to the brake shoes in a drum brake system. The primary shoe is located at the front of the vehicle and is the first to make contact with the drum, while the secondary shoe is positioned at the rear and provides additional braking force.
Step-by-step explanation:
In an adjuster assembly, the primary and secondary shoes refer to the brake shoes or components of a drum brake system.
The primary shoe is the leading shoe, which is located towards the front of the vehicle. It is the first shoe to make contact with the drum when the brakes are applied.
The secondary shoe, or trailing shoe, is positioned towards the rear of the vehicle. It follows the primary shoe and helps generate additional braking force when the brakes are engaged.