Home › CDL Practice Tests › Air Brakes Questions › Question 124
What energy source makes spring brakes trustworthy even after a vehicle sits parked for a long time with all air leaked away?
- A.The battery maintaining pressure
- B.Residual pressure that never leaks
- C.The weight of the cargo alone
- D.The mechanical force of the compressed spring itself, which needs no air, fuel, or electricity to keep holding
Correct answer
D. The mechanical force of the compressed spring itself, which needs no air, fuel, or electricity to keep holding
Why
Time defeats air pressure but not a steel spring, which is why a long-parked trailer is still braked when its tanks read zero. That staying power is exactly what a parking brake must have.
Manual topic: Air Brakes - Spring Brakes and Parking Brakes · From the Air Brakes practice bank (AB-124).