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The air brakes endorsement applies to applicants who wish to drive a vehicle with air brakes in Class A, B, or C CDL. To drive a vehicle with air brakes, you must pass the air brake component of the Missouri CDL knowledge test. The MO CDL air brakes test consists of 25 questions, and you'll need at least 20 correct answers to pass (80%). The test covers the information found in the air brakes section of the Missouri CDL Manual. Take this MO CDL practice test now to prepare for the actual air brakes test!
1. Most heavy-duty vehicles use:
triple air brake systems.
dual air brake systems.
single air brake systems.
2. During a trip you should check:
pressure gauges.
temperature gauges.
All of the above.
3. Emergency brakes are:
not required on doubles.
required on all vehicles.
not required on buses.
4. In vehicles with air brakes, the two markings on a front brake limiting valve are:
left and right.
high and low.
normal and slippery.
5. Which of the following is not a way to know when to change gears?
Use road speed (mph)
Check that the pressure gauge shows normal oil pressure
Use engine speed (rpm)
6. To check that spring brakes come on automatically, the first thing to do is to:
release the parking brake, move the vehicle forward slowly, and apply the brakes firmly.
continue to step on and off the brake pedal until the air pressure falls to the manufacturer’s specification.
turn off the engine, release the parking brake and time the air pressure drop.
7. Brake lag is:
the amount of air pressure required to stop the vehicle.
the distance your vehicle will travel, in ideal conditions, while you are braking.
the time required for the air brakes to work after the brake pedal is pushed.
8. If are being followed closely, you should:
change lanes quickly.
decrease your following distance.
increase your following distance.
9. Which of the following is NOT a reason for hydraulic brake failure?
Stab braking
Brake fade on long hills
Loss of hydraulic pressure
10. To prevent drowsiness you should:
get adequate sleep before a trip.
never drive with a passenger.
schedule trips for the middle of the night.
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MO CDL Air Brakes Test

Number of questions: 25
Correct answers to pass:20
Passing score:80%
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