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Wyoming Air Brakes CDL Practice Test

Below are 25 exam-style questions for the Wyoming Air Brakes CDL knowledge test, modeled on the FMCSA-aligned content used by the Wyoming Department of Transportation. 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.

Heads up: this is a study tool, not a graded exam. Cover the answer with your hand or a sheet of paper for an honest practice run, then re-read the explanations for any questions you missed. Aim for 22 out of 25 or better, three times in a row, before scheduling the real exam.
Question 1 of 25
Spring brakes are held off by:
  • A Engine vacuum
  • B Air pressure
  • C Electrical current
  • D Hydraulic pressure
Correct answer: B
Compressed air holds the springs back. When air pressure drops, the springs apply the brakes mechanically.
Question 2 of 25
After parking a tractor-trailer:
  • A Set both tractor and trailer parking brakes
  • B Leave both released
  • C Set only the trailer parking brake
  • D Set only the tractor parking brake
Correct answer: A
Federal practice is to set both parking brakes when fully parked. The exception is during coupling/uncoupling, where the trailer brakes are set.
Question 3 of 25
The air compressor governor controls:
  • A Brake pad wear
  • B Coolant temperature
  • C When the air compressor will pump air into the storage tanks
  • D Engine RPM
Correct answer: C
The governor cuts the compressor in (start pumping) at low pressure and cuts it out (stop pumping) at high pressure to maintain a working range.
Question 4 of 25
When applying the foot brake hard:
  • A The compressor cuts out
  • B Air pressure may drop slightly
  • C Air pressure should remain unchanged
  • D Air pressure increases
Correct answer: B
A small drop is expected during heavy application. The compressor recharges the system back up to cut-out pressure.
Question 5 of 25
A driver should never:
  • A Test the parking brake
  • B Drain the wet tank
  • C Make pre-trip inspections
  • D Use the trailer hand valve as a parking brake
Correct answer: D
The trailer hand valve is not a parking device — see the trailer-hand-valve question. Always set the trailer parking brakes.
Question 6 of 25
On a vehicle with dual air brakes, the warning device must come on before pressure in either system drops below:
  • A 20 psi
  • B 60 psi
  • C Never; only the gauge needs to read it
  • D 40 psi
Correct answer: B
The low-air warning must activate before pressure drops below 60 psi in either circuit.
Question 7 of 25
If air pressure drops in the emergency line:
  • A Tractor brakes apply
  • B Nothing happens
  • C Trailer service brakes apply
  • D Trailer spring brakes apply automatically
Correct answer: D
Loss of supply-line pressure is the failsafe that triggers the trailer's spring brakes.
Question 8 of 25
The air compressor is driven by:
  • A The transmission
  • B The exhaust system
  • C The electrical system
  • D The engine, by belts or directly geared
Correct answer: D
Compressors are typically engine-driven, either by a belt or direct gearing, so air pressure builds whenever the engine runs.
Question 9 of 25
Air dryers are used in air-brake systems to:
  • A Cool the air before it enters the brake chambers
  • B Increase pressure
  • C Remove moisture and contaminants from the compressed air
  • D Replace governors
Correct answer: C
Dryers reduce moisture in the air system, helping prevent corrosion, ice in winter, and contamination.
Question 10 of 25
You should test the service brakes by:
  • A Pumping the brakes
  • B Driving at 30 mph and slamming on the brakes
  • C Listening to the air gauge
  • D At about 5 mph, applying the brake firmly and feeling for pulling, sticking, or unusual feel
Correct answer: D
A low-speed brake test catches sticking, pulling, or weak brakes before you build up speed.
Question 11 of 25
Glad-hand seals should be:
  • A Free of dirt and damage and properly seated
  • B Loose for easy connection
  • C Coated with oil
  • D Removed for inspection
Correct answer: A
Damaged or dirty seals cause leaks. Inspect and clean them as part of the trailer hookup.
Question 12 of 25
When doing the air-leak rate test, the engine should be:
  • A Running at high RPM
  • B In gear
  • C Started and stopped repeatedly
  • D Off, with brakes released for the first part
Correct answer: D
Engine off, brakes released to test static leak rate; then brakes applied and held for the second part.
Question 13 of 25
After releasing the parking brake on a tractor, you should:
  • A Wait for full system pressure before moving
  • B Drive immediately
  • C Pump the service brake five times
  • D Drain the wet tank
Correct answer: A
Make sure the system reaches at least the cut-out pressure (typically around 120 psi) before driving.
Question 14 of 25
Anti-lock braking systems (ABS) on air-brake vehicles:
  • A Replace foundation brakes
  • B Are required only on hazmat trailers
  • C Help prevent wheel lockup but do not necessarily shorten stopping distance
  • D Are optional and rarely installed
Correct answer: C
ABS helps the driver maintain steering control by preventing wheel lockup. It does not necessarily reduce stopping distance.
Question 15 of 25
Air pressure should normally build from 50 to 90 psi within:
  • A About 3 minutes in dual systems
  • B It does not matter
  • C Less than 30 seconds
  • D 10 minutes
Correct answer: A
Dual air systems should build from 50 to 90 psi within about 3 minutes at idle.
Question 16 of 25
In a combination vehicle, with the brakes applied and the engine off, the maximum allowable air loss is:
  • A 5 psi per minute
  • B 2 psi per minute
  • C 3 psi per minute
  • D 4 psi per minute
Correct answer: D
Combination vehicle, brakes applied: 4 psi per minute. Single vehicle, brakes applied: 3 psi per minute.
Question 17 of 25
The air-brake hand valve (trolley valve) operates:
  • A The trailer service brakes only
  • B The parking brake
  • C Both tractor and trailer brakes
  • D The tractor service brakes only
Correct answer: A
The hand valve applies only the trailer service brakes. It is not a parking brake or a substitute for the foot brake.
Question 18 of 25
A common reason for compressor failure to keep up is:
  • A A broken governor
  • B A clogged air filter or worn compressor
  • C All of the above
  • D A leak in the brake system
Correct answer: C
Any of these causes can prevent the compressor from maintaining cut-out pressure.
Question 19 of 25
A common cause of an air-brake skid is:
  • A Neither of the above
  • B Locking the wheels by braking too hard
  • C Driving too fast for conditions
  • D Both of the above
Correct answer: D
Skids result when the wheel locks and the tire loses traction. Speed and over-application are both common contributors.
Question 20 of 25
Stopping a vehicle with an air-brake failure can sometimes be done by:
  • A Honking
  • B Coasting in neutral
  • C Using the trailer hand valve, then engine braking, then a runaway ramp if needed
  • D Putting the transmission in reverse
Correct answer: C
In an air-brake failure, the trailer hand valve can still apply the trailer service brakes, then engine braking and a runaway ramp.
Question 21 of 25
In a single-vehicle air-brake check with the engine off and brakes released, the maximum allowable air loss is:
  • A 5 psi per minute
  • B 1 psi per minute
  • C 3 psi per minute
  • D 2 psi per minute
Correct answer: D
Single vehicle, brakes released: not more than 2 psi per minute. Combination vehicle: 3 psi per minute.
Question 22 of 25
You should NOT drain the wet tank when:
  • A There is no situation in which draining is wrong
  • B The vehicle is in motion
  • C You are about to begin a trip
  • D It is full of moisture
Correct answer: A
Daily draining is a routine task; there is no situation where draining is unsafe (other than while driving).
Question 23 of 25
You should test the trailer service brakes by:
  • A Pumping them while parked
  • B Listening for a hiss
  • C Looking at the gauge
  • D Releasing the parking brakes, moving the vehicle slowly forward, and applying the trailer hand valve
Correct answer: D
A low-speed pull-and-stop with the trailer hand valve confirms the trailer brakes apply on their own.
Question 24 of 25
A brake check ahead of a downgrade should be done:
  • A At the bottom only
  • B In the middle of the descent
  • C Before reaching the top, while still on level ground
  • D Once a year
Correct answer: C
A brief brake test on level ground at the top reveals problems while you can still stop safely.
Question 25 of 25
Air-brake hoses should:
  • A Show no signs of damage, leaks, or excessive wear
  • B Be wrapped in tape
  • C Have at least 5 splices each
  • D Be coiled tightly under the truck
Correct answer: A
Damaged or chafed hoses are a common air-brake defect and a frequent out-of-service citation.

Study tips for the Wyoming Air Brakes exam

The Air Brakes portion of the Wyoming CDL exam is graded out of the bank of questions the Wyoming Department of Transportation draws from each year. While the exact bank is not published, every question is sourced from the Air Brakes chapter of the Wyoming 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 Wyoming 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 Wyoming Department of Transportation 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 Wyoming 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 Wyoming 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 Wyoming Department of Transportation office.

Already comfortable with this endorsement? Drill another: WY General Knowledge · WY Combination Vehicles · WY Hazardous Materials · WY Passenger · WY School Bus · WY Tank Vehicle · WY Doubles / Triples

New to the CDL process in Wyoming? Read How to apply for a CDL in Wyoming for the document checklist and step-by-step timeline.