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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 Carolina CDL knowledge test. The SC 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 Carolina CDL Manual. Take this SC CDL practice test now to prepare for the actual air brakes test!
1. Parking brakes are:
required on all vehicles.
not required on commercial vehicles with air brakes.
not required on buses.
not required on trailers.
2. 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.
5 mph
20 mph
10 mph
15 mph
3. If your truck has automatic transmission, you should downshift:
after entering a curve.
whenever road conditions allow.
when you need to accelerate.
when going down grades.
4. Air brakes use ________ to make the brakes work.
compressed oil
compressed air
compressed gases
compressed gas cylinders
5. The s-cam:
helps ensure that air flows to all trailers.
forces the brake shoes away from one another and presses them against the inside of the brake drum.
pulls the brake shoes away from the drum.
All of the above.
6. The ________ brake system applies and releases the brakes when the driver uses the brake pedal during normal driving.
7. Which of the following is NOT TRUE? When you drive a tractor-trailer combination with ABS, you should:
drive slower to keep your vehicle in a straight line.
use only the braking force necessary to stop safely.
brake the same way, regardless of whether you have ABS on the tractor, the trailer, or both.
monitor your tractor and trailer as you slow down, and if it is safe to do so, back off the brakes to stay in control.
8. You are coming down a long, steep downgrade. Which of the following is a sign that your brakes may have started to fade?
The steering feels heavy.
You have to apply your brakes harder and harder to get the same stopping power.
You hear a loud "bang".
The brake pedal feels spongy or goes to the floor.
9. What should you do to correct a drive-wheel braking skid?
Fully apply the brakes, turn the steering wheel quickly, push in the clutch, and countersteer.
Turn in the same direction as the skid.
Stop braking, turn the steering wheel quickly, push in the clutch, and countersteer.
None of the above.
10. Air pressure should build up in a single air system, within about:
10 minutes.
3 minutes.
15 minutes.
1 minute.
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SC CDL Air Brakes Test

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