While travelling downhill, you notice that each time you want to brake, you must press the brake pedal farther down than the last time to achieve the same braking force. What could be causing this?
- A faulty air compressor governor
- A too-slow air compressor
- A jammed foot brake pedal
- Brake fade ✓
Answer: D. Brake fade
The likely cause is brake fade: the brakes lose effectiveness as they heat up, so you need to press harder or farther to get the same braking force.
Why this is the answer
The air brake handbook explains that as brake components heat up, their effectiveness drops. The driver then has to push harder on the pedal to develop the same brake force, and that condition is called brake fade. It becomes more noticeable on long downhill runs, especially at excessive speed or with an overloaded vehicle. The repeated need for more pedal effort fits that heat-related loss of braking force, so brake fade is the cause the handbook points to.
Why the other answers are wrong
- A. A faulty air compressor governor — A faulty air compressor governor is not described in the passages as producing this progressive loss of braking force; the handbook ties it to brake fade.
- B. A too-slow air compressor — A too-slow air compressor is not presented as the cause of needing progressively more pedal to get the same braking force; the relevant passage is about heat-related brake fade.
- C. A jammed foot brake pedal — A jammed foot brake pedal is not the condition described; the passages describe a gradual heat-related reduction in braking effectiveness that requires more pedal pressure.
Remember it
When downhill braking keeps asking for more pedal, think hot brakes fading, not a stuck pedal.