Home › CDL Practice Tests › Air Brakes Questions › Question 96
What holds the spring brakes in the released (off) position during normal driving?
- A.A cable the driver ties in the cab
- B.Air pressure in the spring brake chamber compresses the powerful spring and keeps the brake off
- C.The weight of the vehicle itself
- D.A magnet on the brake drum
Correct answer
B. Air pressure in the spring brake chamber compresses the powerful spring and keeps the brake off
Why
Spring brakes are backwards from service brakes: air works to release them, not apply them. That is why losing air does not mean losing all brakes, it means the springs take over.
Manual topic: Air Brakes - Spring Brakes and Parking Brakes · From the Air Brakes practice bank (AB-096).