What determines the efficiency of the spring parking brake?
- The service brake adjustment ✓
- The alignment of the wheels
- The tire pressure
- The road conditions
Answer: A. The service brake adjustment
The efficiency of the spring parking brake is determined by the service brake adjustment.
Why this is the answer
The handbook says spring parking brakes can apply when air pressure drops, but how well they stop or hold the vehicle depends on keeping the brakes properly adjusted. The spring brake works through the normal service chamber pushrod and slack adjuster, so brake adjustment affects how well the spring force is applied. That is why the correct choice is the one about service brake adjustment, not wheel alignment, tire pressure or road conditions.
Why the other answers are wrong
- B. The alignment of the wheels — Wheel alignment is not described in the handbook as a factor in spring parking brake efficiency.
- C. The tire pressure — Tire pressure is not described in the handbook as determining how well the spring parking brake works.
- D. The road conditions — Road conditions are not described in the handbook as determining the efficiency of the spring parking brake itself.
Remember it
The spring supplies the force, but brake adjustment decides how well that force reaches the brakes.