Home › CDL Practice Tests › Combination Vehicles Questions › Question 152
Why should you never try to 'hold' a jackknifing trailer straight by applying the trailer hand valve hard?
- A.The hand valve cannot produce any braking force at highway speed
- B.Hard trailer braking is often what locked the trailer wheels in the first place, so more of it makes the swing worse
- C.Using the hand valve turns off the tractor's steering
- D.The hand valve releases all air from the tractor tanks instantly
Correct answer
B. Hard trailer braking is often what locked the trailer wheels in the first place, so more of it makes the swing worse
Why
If trailer wheel lockup started the skid, adding more trailer brake only keeps those wheels locked and sliding. Recovery comes from letting the wheels roll again, not from braking the swinging unit harder.
Manual topic: Combination Vehicles - Skids and Jackknifing · From the Combination Vehicles practice bank (CV-152).