Minnesota Air Brakes CDL Practice Test
Below are 25 exam-style questions for the Minnesota Air Brakes CDL knowledge test, modeled on the FMCSA-aligned content used by the Minnesota Driver and Vehicle Services. Try to answer each question on your own before reading the answer key directly under it. The questions and answer choices are shuffled deterministically per state and endorsement, so the order will stay the same on repeat visits — that lets you genuinely measure your improvement.
- A Pumping the brakes
- B At about 5 mph, applying the brake firmly and feeling for pulling, sticking, or unusual feel
- C Listening to the air gauge
- D Driving at 30 mph and slamming on the brakes
- A The compressor cuts out
- B Air pressure may drop slightly
- C Air pressure increases
- D Air pressure should remain unchanged
- A It violates federal weight law
- B It will reduce engine power
- C It can damage the rubber seals
- D It is bad luck
- A Releasing the parking brakes, moving the vehicle slowly forward, and applying the trailer hand valve
- B Listening for a hiss
- C Pumping them while parked
- D Looking at the gauge
- A 60 psi
- B 20 psi
- C 40 psi
- D Never; only the gauge needs to read it
- A Heat from continuous brake use on long downgrades
- B Too much air pressure
- C Worn-out hoses
- D Cold weather
- A Coolant temperature
- B Engine RPM
- C When the air compressor will pump air into the storage tanks
- D Brake pad wear
- A It is full of moisture
- B The vehicle is in motion
- C There is no situation in which draining is wrong
- D You are about to begin a trip
- A Disconnect the trailer
- B Continue driving — you still have normal brakes — and have the system checked at the next opportunity
- C Immediately stop on the side of the road
- D Pump the brakes hard
- A All of the above
- B A leak in the brake system
- C A broken governor
- D A clogged air filter or worn compressor
- A Stay popped out and yellow
- B Stay pushed in
- C Have no indication
- D Flash red
- A It does not matter
- B About 3 minutes in dual systems
- C 10 minutes
- D Less than 30 seconds
- A Only an electrical connector
- B Service line and emergency line, with glad-hand connectors
- C One additional reservoir for the trailer brakes
- D Only a safety chain
- A A new compressor
- B A leak or restriction
- C A worn seat belt
- D Normal operation
- A At the bottom only
- B Before reaching the top, while still on level ground
- C Once a year
- D In the middle of the descent
- A The transmission
- B The electrical system
- C The engine, by belts or directly geared
- D The exhaust system
- A 1 psi
- B 10 psi
- C 2-3 psi
- D 5 psi
- A Putting the transmission in reverse
- B Coasting in neutral
- C Using the trailer hand valve, then engine braking, then a runaway ramp if needed
- D Honking
- A They control trailer height
- B Out-of-adjustment slack adjusters can result in brakes that do not work properly
- C They are decorative
- D They affect engine performance
- A 60 psi
- B 85 psi
- C 40 psi
- D 125 psi
- A It will activate the spring brakes
- B It only works while the engine is running
- C Air leaks could cause the brakes to release and let the vehicle roll
- D It is illegal
- A Increase engine RPM
- B Continue to the next exit
- C Bring the vehicle to a safe stop as soon as possible and find the cause
- D Pump the brakes to keep pressure
- A Test the parking brake
- B Use the trailer hand valve as a parking brake
- C Make pre-trip inspections
- D Drain the wet tank
- A Coast in neutral
- B Test the brakes at the bottom
- C Test the brakes by lightly applying them at the top
- D Skip the brake test
- A 2 psi per minute
- B 4 psi per minute
- C 5 psi per minute
- D 3 psi per minute
Study tips for the Minnesota Air Brakes exam
The Air Brakes portion of the Minnesota CDL exam is graded out of the bank of questions the Minnesota Driver and Vehicle Services draws from each year. While the exact bank is not published, every question is sourced from the Air Brakes chapter of the Minnesota CDL handbook, which itself is derived from the FMCSA Model Commercial Driver's License Manual. That means studying our practice tests, reading the corresponding handbook chapter, and re-reading the parts you got wrong is genuinely the most efficient route to a first-time pass.
Most successful applicants follow a simple cycle: take the practice test cold, write down every question you missed, open the matching chapter of the official Minnesota handbook, re-read the section that contains the right answer, then re-take the practice test 24 to 48 hours later. The 24-hour delay matters — sleep is when your brain commits new information to long-term memory, and CDL knowledge questions reward that kind of consolidated learning rather than cramming.
Pay particular attention to questions that include qualifier words like always, never, only, primary, or most. CDL test writers love to flip the right answer with a single qualifier. When two answer choices look almost identical, pay attention to the verb (is it must, should, or may?) and to any numbers (14 days, 100 air miles, 8 hours, 70/8 split). On endorsement tests in particular, watch for trick framing where a true statement about a different endorsement is offered as the "correct" answer to a question that is actually about Air Brakes.
Test-day logistics matter too. Bring photo ID, your Social Security card or birth certificate, your medical examiner's certificate (DOT card), and proof of state residency if you haven't already submitted those documents. The Minnesota Driver and Vehicle Services will not let you sit for the knowledge exam without your documentation, and most offices charge an additional fee for re-attempts. Arrive early — the wait at most CDL testing offices runs 30 to 60 minutes — and silence your phone before the exam begins.
Finally, keep your General Knowledge fundamentals sharp even when you're focused on the Air Brakes exam. Many states administer multiple knowledge tests in a single sitting, and questions on weight definitions (GVWR, GCWR, GAWR), stopping distance, and the pre-trip inspection routine show up across endorsements. If you're unsure on the basics, sit a fresh Minnesota General Knowledge practice test before scheduling the real exam.
Next steps
Missed more than four questions? Re-read the Air Brakes study guide and the matching chapter in the official Minnesota CDL handbook. Then come back and re-take the test. Once you can score 22 of 25 or higher on three runs in a row, you're in good shape to schedule the real exam at your local Minnesota Driver and Vehicle Services office.
Already comfortable with this endorsement? Drill another: MN General Knowledge · MN Combination Vehicles · MN Hazardous Materials · MN Passenger · MN School Bus · MN Tank Vehicle · MN Doubles / Triples
New to the CDL process in Minnesota? Read How to apply for a CDL in Minnesota for the document checklist and step-by-step timeline.