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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 South Dakota CDL knowledge test. The SD 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 South Dakota CDL Manual. Take this SD CDL practice test now to prepare for the actual air brakes test!
1. To test the air leakage rate, with a fully-charged air system you should ____________ and time the air pressure drop.
check the air compressor's drive belt, chock the wheels
turn off the engine, release the parking brake
put alcohol into the air system, run the engine at a fast idle
release the parking brake, leave the engine running
2. To check the slack adjusters on S-cam brakes, you should:
park on level ground and fan off the air pressure by rapidly applying and releasing the foot brake.
release the parking brake valve and begin reducing the air pressure by stepping on and off the brake pedal.
park on level ground, chock the wheels and release the parking brakes, then use gloves and pull hard on each slack adjuster that you can reach.
All of the above.
3. The emergency brake system:
uses parts of the service and parking brake systems to stop the vehicle in the event of a brake system failure.
uses the service brake to stop the vehicle in the event of a parking brake system failure.
uses the parking brake to stop the vehicle in the event of a brake system failure.
None of the above.
4. When parking a trailer without spring brakes, it is very important for safety that you use wheel chocks. Why?
The air could leak out of the trailer air tank, releasing its emergency brakes.
You may not notice a major leak in the service line until you try to put the brakes on.
if you don't use wheel chocks, supply air will be sent to the service line instead of going to charge the trailer air tanks.
None of the above.
5. You are going down a steep grade. Once the vehicle is in the proper low gear, you should brake just hard enough to feel a slowdown, and then release the brakes when your speed has been reduced to ____ below your safe speed.
20 mph
15 mph
10 mph
5 mph
6. Most heavy duty vehicles use ___ air brake systems for safety.
7. An Anti-lock Braking System (ABS):
always shortens your stopping distance.
lets you drive faster.
increases your normal braking capability.
keeps your wheels from locking up when you brake hard.
8. The trailer hand valve should:
be used in driving.
never be used to test the trailer brakes.
never be used for parking.
All of the above.
9. In vehicles with air brakes, water and compressor oil in the bottom of the air tank:
should be drained completely.
should be added regularly.
should not be removed.
None of the above.
10. To check the slack adjusters:
park downhill and see if the vehicle rolls.
Park on level ground and chock the wheels, release the parking brakes and pull hard on each slack adjuster. The slack adjuster shouldn't move more than one inch.
check the air hoses connected to the brake chambers to make sure they aren't cut or worn.
None of the above.
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SD Air Brakes CDL Test

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