Manitoba Airbrake Practice Exam

At what pressure do the spring brakes normally start to apply due to insufficient pressure to keep them released?

1. 40 psi

2. 60 psi

3. 80 psi

4. 100 psi

The correct answer is: 60 psi

When a vehicle's air system reaches a pressure of 60 psi or below, the spring brakes will typically begin to apply. This is because the spring brakes are designed to engage when there is insufficient pressure to keep them released, as a safety measure in case of air system failure. Options A, C, and D are incorrect because they fall outside of this pressure range and would not trigger the spring brakes to engage. Option A is too low, meaning the spring brakes would apply prematurely, potentially causing unnecessary wear on the brakes. Options C and D are too high, meaning the spring brakes would not engage until the air pressure reaches a critical and potentially dangerous level.