In a dual air-brake system, the time required for air pressure to build from 85 to 100 psi should be no more than:
Correct. In dual air-brake systems, air should build from 85 to 100 psi within 45 seconds at engine governed RPM.
CDL Practice Question #108
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.