Minnesota Air Brakes Practice Test

Required if the vehicle you'll drive has air brakes — which in practice means nearly every combination vehicle and most straight trucks. The test covers the parts of an air-brake system (compressor, governor, tanks, valves), the specific pressures where things happen (cut-in, cut-out, low-air warning, spring-brake pop-out), and the inspection sequence for leaks and warning devices. Fail this knowledge test or take the skills test in a vehicle without air brakes, and your license carries an air-brake restriction that keeps you out of most trucking jobs.

Who needs it: Anyone who'll drive a vehicle with air brakes. Skipping it puts an L or Z restriction on the license.

Sample practice questions

Brake fade is caused mainly by:

Answer: Excessive heat from overusing the brakes — Excess heat changes the linings and expands the drums, reducing braking; rely on engine braking to avoid it.

In a dual air system, pressure should build from 85 to 100 psi within:

Answer: 45 seconds — Dual systems should build 85→100 psi within 45 seconds at operating rpm.

At about what pressure does the governor stop the compressor from pumping (cut-out)?

Answer: 125 psi — Cut-out is about 125 psi. Cut-in is about 100 psi; 150 psi is the safety valve; 60 psi is the low-air warning.

Common mistakes on the Air Brakes test

  • Mixing up the pressure numbers — cut-out (~125 psi), cut-in (~100 psi), low-air warning (~60 psi) are all tested
  • Confusing spring brakes (parking/emergency) with service brakes — which system does what, and when
  • Forgetting the air-leak rate limits for the applied and released tests during inspection
  • Assuming ABS changes how you brake — the test wants normal braking with ABS, not pumping

Studying with the full Truckcess course does double duty: the theory counts toward the federal ELDT requirement (Truckcess is listed on the FMCSA Training Provider Registry).

Official source: Minnesota Driver and Vehicle Services (Department of Public Safety)

CDL licensing in Minnesota is administered by the Minnesota Driver and Vehicle Services (Department of Public Safety). Fees, scheduling, forms, and the official Minnesota CDL manual live on the official site: Minnesota DVS — official CDL page (verified 2026-08-09).

Truckcess is not affiliated with or endorsed by the Minnesota Driver and Vehicle Services (Department of Public Safety). Our practice tests cover the federal CDL knowledge standards (49 CFR Part 383) that every state exam is built on; exact question counts, fees, and procedures vary by state and change over time — the official site is always the authority.

More Minnesota practice tests

Full prep courses are one-time from $59 with 12 months of access — mytruckcess.com/cdl.

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