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Why should you avoid fanning the brakes (repeatedly applying and releasing) on a long downgrade?
- A.Fanning makes the trailer brakes apply before the tractor brakes
- B.Fanning is only a problem when the trailer is empty
- C.Fanning uses up air faster than the compressor can replace it, and the brakes can fade or be lost when pressure drops too far
- D.Fanning locks the trailer ABS into test mode
Correct answer
C. Fanning uses up air faster than the compressor can replace it, and the brakes can fade or be lost when pressure drops too far
Why
Each application spends air, and repeated fanning can pull tank pressure down while also heating the brakes. The correct downgrade technique is to select the right gear and use firm snub applications, then release to let the brakes cool.
Manual topic: Combination Vehicles - Skids and Jackknifing · From the Combination Vehicles practice bank (CV-139).