Air Brakes · Question #72

How much pressure should be lost in one minute with the engine off and brakes applied (combination)?

A. No more than 4 psi
B. 10 psi
C. 6 psi
D. 2 psi

Correct answer: A. No more than 4 psi
Explanation: Applied leakage limit: 3 psi single, 4 psi combination per minute.

Why this question matters on the Air Brakes exam

This question is one of the 65 we have for the Air Brakes CDL knowledge test. The official AAMVA Commercial Driver License Manual chapter on Air Brakes covers exactly this topic, and most state DMV exams pull from the same chapter. Memorizing the right answer is fine for passing, but understanding the underlying rule is what keeps you safe on the road and out of trouble with FMCSA inspectors.

If this topic gave you trouble, take the full Air Brakes practice test to drill it across all the related questions. We recommend reading every explanation, even on the questions you got right, because the manual phrasing in the explanation often shows up word-for-word on the real exam.

Take the full Air Brakes practice test →