Home › CDL Practice Tests › Air Brakes Questions › Question 97
What applies the spring brakes when they engage?
- A.A heavy mechanical spring, once air pressure holding it back is removed or falls too low
- B.Hydraulic fluid from the master cylinder
- C.The driver's hand lever alone
- D.Electric current from the alternator
Correct answer
A. A heavy mechanical spring, once air pressure holding it back is removed or falls too low
Why
The spring stores the energy that applies the brake, so no air or electricity is needed to make it work. This purely mechanical application is the heart of the fail-safe design.
Manual topic: Air Brakes - Spring Brakes and Parking Brakes · From the Air Brakes practice bank (AB-097).