Tennessee Air Brakes CDL Practice Test
Below are 25 exam-style questions for the Tennessee Air Brakes CDL knowledge test, modeled on the FMCSA-aligned content used by the Tennessee Department of Safety and Homeland Security. 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 0 feet
- B 32 feet
- C 300 feet
- D 142 feet
- A Tractor brakes apply
- B Trailer service brakes apply
- C Nothing happens
- D Trailer spring brakes apply automatically
- A 2 psi per minute
- B 4 psi per minute
- C 3 psi per minute
- D 5 psi per minute
- A Only a safety chain
- B One additional reservoir for the trailer brakes
- C Service line and emergency line, with glad-hand connectors
- D Only an electrical connector
- A They control trailer height
- B They are decorative
- C Out-of-adjustment slack adjusters can result in brakes that do not work properly
- D They affect engine performance
- A Replace governors
- B Cool the air before it enters the brake chambers
- C Increase pressure
- D Remove moisture and contaminants from the compressed air
- A Help prevent wheel lockup but do not necessarily shorten stopping distance
- B Replace foundation brakes
- C Are optional and rarely installed
- D Are required only on hazmat trailers
- A The horn
- B The service brakes for normal stops
- C The tail lights
- D The headlights
- A The engine stops
- B The trailer hand valve releases
- C Spring brakes apply automatically
- D Nothing happens until you stop
- A You are about to begin a trip
- B The vehicle is in motion
- C There is no situation in which draining is wrong
- D It is full of moisture
- A A normal feature
- B Caused by overuse
- C A serious defect that can prevent backup braking
- D Required by federal law
- A A clogged air filter or worn compressor
- B A leak in the brake system
- C All of the above
- D A broken governor
- A Normal operation
- B A worn seat belt
- C A new compressor
- D A leak or restriction
- A They must be drained daily to remove water and oil
- B They never need to be drained
- C They must be drained completely once a year
- D They drain themselves automatically in all trucks
- A Once a year
- B At the bottom only
- C In the middle of the descent
- D Before reaching the top, while still on level ground
- A Worn-out hoses
- B Heat from continuous brake use on long downgrades
- C Too much air pressure
- D Cold weather
- A 60 psi
- B Never; only the gauge needs to read it
- C 40 psi
- D 20 psi
- A 3 psi per minute
- B 1 psi per minute
- C 5 psi per minute
- D 2 psi per minute
- A Have small cracks
- B Be glowing red after stops
- C Be free of cracks longer than half the width of the friction area
- D Be coated with oil
- A Two governors
- B Two compressors
- C Twice the air pressure
- D Two separate air-brake systems on one set of brake controls
- A Engine overheating
- B Steering wander
- C Wheel lockup during emergency braking
- D Tire blowouts
- A Make pre-trip inspections
- B Test the parking brake
- C Drain the wet tank
- D Use the trailer hand valve as a parking brake
- A It only works while the engine is running
- B Air leaks could cause the brakes to release and let the vehicle roll
- C It is illegal
- D It will activate the spring brakes
- A Started and stopped repeatedly
- B Running at high RPM
- C Off, with brakes released for the first part
- D In gear
- A Be wrapped in tape
- B Have at least 5 splices each
- C Be coiled tightly under the truck
- D Show no signs of damage, leaks, or excessive wear
Study tips for the Tennessee Air Brakes exam
The Air Brakes portion of the Tennessee CDL exam is graded out of the bank of questions the Tennessee Department of Safety and Homeland Security draws from each year. While the exact bank is not published, every question is sourced from the Air Brakes chapter of the Tennessee 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 Tennessee 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 Tennessee Department of Safety and Homeland Security 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 Tennessee 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 Tennessee 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 Tennessee Department of Safety and Homeland Security office.
Already comfortable with this endorsement? Drill another: TN General Knowledge · TN Combination Vehicles · TN Hazardous Materials · TN Passenger · TN School Bus · TN Tank Vehicle · TN Doubles / Triples
New to the CDL process in Tennessee? Read How to apply for a CDL in Tennessee for the document checklist and step-by-step timeline.