Home › CDL Practice Tests › Air Brakes Questions › Question 187
Why does vehicle speed matter so much when judging how hard a downgrade is on the brakes?
- A.Speed has no effect if the gear is correct
- B.Faster descent means the brakes must absorb much more energy in a shorter time, so heat builds far more quickly
- C.Brakes absorb the same heat at any speed
- D.Slower speeds always overheat brakes faster
Correct answer
B. Faster descent means the brakes must absorb much more energy in a shorter time, so heat builds far more quickly
Why
The energy a moving truck carries grows rapidly with speed, and on a grade gravity keeps adding more. Holding a lower safe speed from the top keeps the heat load within what engine braking and snub applications can manage.
Manual topic: Air Brakes - Downgrade Braking · From the Air Brakes practice bank (AB-187).