Air-brake adjustment is critical because out-of-adjustment brakes:
Correct. Out-of-adjustment slack adjusters reduce braking force at the wheel, increasing stopping distance and risking brake failure on long downgrades.
CDL Practice Question #165
Category: Air Brakes
Why this question matters
This question is one of 71 in our Air Brakes bank. The reasoning above comes directly from the AAMVA CDL Manual, the source document used by every U.S. state DMV. Memorizing the underlying rule — not just the letter answer — is what separates passing on the first attempt from a return trip and another fee.