CDL General Knowledge TestAir Brakes (if applicable)Hard
During a pre-trip inspection, a driver notices that the brake pedal on their air brake equipped vehicle has no 'free play' or 'dead travel' when initially pressed. What could this indicate?
- AThe air compressor is malfunctioning.
- BThe brake pedal is binding or the linkage is seized.
- CThe brake linings are excessively worn.
- DThe slack adjusters are properly adjusted.
Show answer & explanationAnswer & explanation
Correct answer: B. The brake pedal is binding or the linkage is seized.
A brake pedal with no 'free play' or 'dead travel' could mean the pedal or its linkage is binding. This can lead to the brakes being partially applied or not fully releasing, causing issues like overheating or premature wear. There should be a small amount of free travel before resistance is felt.
Why the other options are wrong
- A. An air compressor malfunction would affect air pressure build-up, not the mechanical free play of the pedal.
- C. Excessively worn linings would typically lead to more pedal travel, not less or none.
- D. Properly adjusted slack adjusters would still allow for normal pedal free play.
Brake Pedal Free Play (Air Brakes)
The initial amount of travel a brake pedal has before resistance is felt and the brake system begins to engage, indicating proper mechanical function of the pedal and linkage.
- A small amount of free play is normal and necessary.
- No free play suggests binding or seized linkage.
- Excessive free play may indicate worn components or poor adjustment.
Memory trick: Free play is good, no play is bad, too much play is also bad.