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What is brake lag, and how is it different from brake fade?
- A.Lag and fade are two names for the same condition
- B.Lag is caused by hot drums and fade by cold drums
- C.Brake lag is the short delay while air travels through the system and the brakes apply, while fade is loss of friction and power from overheated brakes
- D.Lag only happens with hydraulic brakes
Correct answer
C. Brake lag is the short delay while air travels through the system and the brakes apply, while fade is loss of friction and power from overheated brakes
Why
Air brakes need a fraction of a second for pressure to reach the chambers and move the parts, and that delay is part of stopping distance. Fade is a separate heat problem where the brakes apply but cannot generate enough friction to slow the vehicle.
Manual topic: Air Brakes - Brake Lag · From the Air Brakes practice bank (AB-189).