CDL Practice Question #164

To check air-brake adjustment quickly, you can:

Measure the slack adjuster pushrod travel; if it has moved more than about 1 inch when brakes are applied at 90+ psi, adjustment is needed
Listen to the sound
Look at the tires
Check the dashboard light

Correct. Pushrod travel beyond about 1 inch (varies by chamber size) indicates an adjustment issue. Use a marked stroke check or have a mechanic verify.

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.

Practice more

Full Air Brakes practice test
Air Brakes study guide
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