CDL Air Brakes Practice Test 2026: Test próbny 2

1. Pytanie 1 z 25

   What is a wig wag?

   • AA type of flashing brake light on the trailer
   • BA device that wags the trailer to warn drivers
   • CA switch that releases the spring brakes
   • DA metal arm that drops into view when air is low
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   Odpowiedź: D. A metal arm that drops into view when air is low

   A wig wag is a low pressure warning device: a mechanical arm that drops into your view when pressure falls below 60 psi.

2. Pytanie 2 z 25

   What does the stop light switch do in an air brake system?

   • ATurns on the brake lights when you brake
   • BApplies the spring brakes when air is low
   • CStops the compressor at cut-out pressure
   • DTurns off the engine when pressure is low
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   Odpowiedź: A. Turns on the brake lights when you brake

   An air-pressure switch turns on the brake lights when the brakes are applied.

3. Pytanie 3 z 25

   Some older vehicles have a front brake limiting valve with a "normal" and "slippery" setting. Where should you keep it?

   • AIt does not matter
   • BIn the "normal" position
   • CIn the "slippery" position at all times
   • DIn "slippery" on dry roads only
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   Odpowiedź: B. In the "normal" position

   The slippery setting cuts air to the front brakes by half, which reduces stopping power. Keep it in normal.

4. Pytanie 4 z 25

   How are spring brakes held off during normal driving?

   • ABy air pressure
   • BBy the parking brake cable
   • CBy the governor
   • DBy hydraulic fluid
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   Odpowiedź: A. By air pressure

   Spring brakes are held back by air pressure. When air is lost, the springs put on the brakes.

5. Pytanie 5 z 25

   When will the spring brakes on a tractor or straight truck come fully on?

   • AWhen air pressure falls below 100 psi
   • BWhen air pressure falls to about 20 to 45 psi
   • CWhen air pressure rises above 125 psi
   • DOnly when the driver pulls the yellow knob
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   Odpowiedź: B. When air pressure falls to about 20 to 45 psi

   Spring brakes come fully on when air pressure drops to a range of 20 to 45 psi, typically 20 to 30 psi.

6. Pytanie 6 z 25

   The low air pressure warning comes on while you are driving. What should you do?

   • APump the brakes to build pressure
   • BSpeed up to charge the tanks faster
   • CStop and park safely as soon as possible
   • DKeep driving to the next terminal
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   Odpowiedź: C. Stop and park safely as soon as possible

   There may be an air leak. Controlled braking is only possible while enough air remains, so stop safely right away.

7. Pytanie 7 z 25

   Why should you not push the brake pedal down when the spring brakes are on?

   • AIt turns off the ABS
   • BThe combined force can damage the brakes
   • CIt will raise the air pressure
   • DIt will release the spring brakes
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   Odpowiedź: B. The combined force can damage the brakes

   Pushing the pedal while the spring brakes are on adds the two forces together and can damage the brakes.

8. Pytanie 8 z 25

   What does the parking brake control look like on newer vehicles?

   • AA green lever beside the seat
   • BA red, eight-sided knob
   • CA blue, round push-pull knob
   • DA yellow, diamond-shaped knob
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   Odpowiedź: D. A yellow, diamond-shaped knob

   Newer vehicles use a yellow, diamond-shaped knob. The red eight-sided knob is the trailer air supply.

9. Pytanie 9 z 25

   How do you use the yellow parking brake knob?

   • APush it in to apply; pull it out to release
   • BPull it out to apply; push it in to release
   • CHold it down for as long as you are parked
   • DTurn it to the left to apply the brakes
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   Odpowiedź: B. Pull it out to apply; push it in to release

   Pull the knob out to put the parking brakes on, and push it in to release them.

10. Pytanie 10 z 25

    What does a modulating control valve let you do?

    • ADrain all the air tanks from inside the cab
    • BApply the spring brakes a little at a time
    • CChange the governor's cut-in and cut-out settings
    • DTurn the antilock brake system on and off
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    Odpowiedź: B. Apply the spring brakes a little at a time

    A modulating control valve is a lever on the dash that lets you apply the spring brakes a little at a time.

11. Pytanie 11 z 25

    Some vehicles have dual parking control valves with a separate small air tank. What is it for?

    • AFilling the tires with air when one goes low
    • BGiving the air horn its own supply of air
    • CReleasing the spring brakes briefly in an emergency
    • DMaking the parking brakes hold more strongly
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    Odpowiedź: C. Releasing the spring brakes briefly in an emergency

    The separate tank holds only enough air to release the spring brakes a few times, so plan your moves carefully.

12. Pytanie 12 z 25

    Truck tractors with air brakes built on or after what date must have antilock brakes (ABS)?

    • AJuly 1, 2010
    • BJanuary 1, 1990
    • CMarch 1, 2005
    • DMarch 1, 1997
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    Odpowiedź: D. March 1, 1997

    Air-braked truck tractors built on or after March 1, 1997 must have ABS. Other air-braked vehicles built on or after March 1, 1998 must too.

13. Pytanie 13 z 25

    Which air-braked vehicles built on or after March 1, 1998 must have ABS?

    • ATrucks, buses, trailers and converter dollies
    • BOnly school buses and transit buses
    • COnly tank vehicles hauling hazmat
    • DOnly truck tractors pulling trailers
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    Odpowiedź: A. Trucks, buses, trailers and converter dollies

    Besides tractors (from March 1, 1997), other air brake vehicles built on or after March 1, 1998 must have antilock brakes.

14. Pytanie 14 z 25

    What does it mean if your ABS lamp comes on for a moment when you start the vehicle and then goes out?

    • AThe ABS has failed
    • BIt is a normal bulb check
    • CThe parking brake is off
    • DThe air tanks are empty
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    Odpowiedź: B. It is a normal bulb check

    Newer systems light the ABS lamp briefly at start-up as a bulb check, then turn it off.

15. Pytanie 15 z 25

    Does ABS shorten your stopping distance?

    • AYes, it always cuts stopping distance in half
    • BYes, but only on dry roads
    • CNo, it makes stopping distance much longer
    • DNot necessarily; it helps you keep steering control
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    Odpowiedź: D. Not necessarily; it helps you keep steering control

    ABS does not change normal braking ability or always shorten stopping distance. It prevents lockup so you can steer.

16. Pytanie 16 z 25

    In a dual air brake system, which brakes does the primary system usually run?

    • AThe front brakes
    • BThe rear brakes
    • COnly the parking brakes
    • DOnly the trailer brakes
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    Odpowiedź: B. The rear brakes

    The primary system usually works the rear axle brakes. The secondary works the front brakes and maybe one rear axle.

17. Pytanie 17 z 25

    Before driving a vehicle with a dual air system, how much pressure should the compressor build in both systems?

    • AAt least 150 psi
    • BAt least 40 psi
    • CAt least 100 psi
    • DAt least 60 psi
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    Odpowiedź: C. At least 100 psi

    Let the compressor build up at least 100 psi in both the primary and secondary systems before driving.

18. Pytanie 18 z 25

    In a dual air system, how quickly should pressure build from 85 to 100 psi at operating rpm?

    • AWithin about 3 minutes
    • BWithin about 45 seconds
    • CWithin about 5 seconds
    • DWithin about 10 minutes
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    Odpowiedź: B. Within about 45 seconds

    In dual systems, pressure should go from 85 to 100 psi within 45 seconds. Larger tanks may take longer; check the specifications.

19. Pytanie 19 z 25

    What is the main job of the slack adjuster?

    • AIt tells the compressor when to pump
    • BIt drains water from the air tanks
    • CIt turns on the brake lights when braking
    • DIt links the push rod to the brake camshaft
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    Odpowiedź: D. It links the push rod to the brake camshaft

    The push rod turns the slack adjuster, which turns the camshaft and S-cam to apply the brakes.

20. Pytanie 20 z 25

    You pull hard on a slack adjuster with the brakes released. How far can it move before it probably needs adjusting?

    • AIt should never move at all, even slightly
    • BAbout one inch where the push rod attaches
    • CAbout one-eighth inch at the end of the arm
    • DAbout six inches at the end of the arm
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    Odpowiedź: B. About one inch where the push rod attaches

    If a slack adjuster moves more than about one inch where the push rod attaches, it probably needs adjustment.

21. Pytanie 21 z 25

    What must you do before checking slack adjusters?

    • ASet the parking brakes and run the engine
    • BRaise the vehicle on a jack so wheels turn
    • CDrain the air tanks completely first
    • DChock the wheels and release the parking brakes
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    Odpowiedź: D. Chock the wheels and release the parking brakes

    To check slack adjusters you must release the parking brakes, so chock the wheels first on level ground.

22. Pytanie 22 z 25

    What is the most common problem found in roadside inspections of air brakes?

    • AMissing reflective triangles
    • BBrakes out of adjustment
    • CEmpty alcohol evaporators
    • DBroken brake lights
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    Odpowiedź: B. Brakes out of adjustment

    Out-of-adjustment brakes are the number one problem inspectors find.

23. Pytanie 23 z 25

    Your vehicle has automatic slack adjusters. Do they still need to be checked?

    • ANo, they adjust themselves
    • BOnly once a year at service
    • CYes, during every inspection
    • DOnly after a crash or a fault
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    Odpowiedź: C. Yes, during every inspection

    Vehicles built since 1994 have automatic slack adjusters, but they must still be checked.

24. Pytanie 24 z 25

    An automatic slack adjuster is out of adjustment. What does this usually mean?

    • AThere is probably a mechanical problem that needs repair
    • BThe tanks need draining
    • CThe governor is set too high
    • DIt just needs a quick manual adjustment and no repair
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    Odpowiedź: A. There is probably a mechanical problem that needs repair

    Manual adjustment of an automatic adjuster is only a temporary emergency fix. Have the vehicle repaired as soon as possible.

25. Pytanie 25 z 25

    How long can a crack in a brake drum be?

    • AAny length, as long as it is not leaking
    • BUp to the full width of the friction area
    • CUp to half the width of the friction area
    • DUp to 6 inches, measured along the drum
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    Odpowiedź: C. Up to half the width of the friction area

    Drum cracks must not be longer than one-half the width of the friction area.

Klawiatura: 1–4, aby odpowiedzieć, Enter – następne pytanie.

Prawdziwy egzamin: Varies by state; usually 25 questions, with 20 correct needed (80%)