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  • Updated for January 2025
  • Based on 2025 SC commercial driver's license manual

Free South Carolina CDL Air Brakes Test 2025

The state of South Carolina relies on its truck drivers to keep the state running, and the best career for a truck drivers in the state is one with the fewest limits possible, which means the ability to drive a truck with or without air brakes. To receive a CDL with an air brakes qualification, taking practice exams is the key to getting a great score on your real exam. This 30 multiple-choice question quiz, with carefully written explanations based on the South Carolina Commercial Driver License Manual, covers all the basics and some advanced topics that you need to know to receive a passing score on your exam. Take it as many times as you need to get a high enough score so that you will be comfortable for your real exam, and you’ll be on your way to a less restricted SC CDL today!

  • Perfect for first-time and renewal CDL/CLP applicants, and those adding endorsements

What you need to know

9 min to complete
Available in EN and ES
Verified by Steven Litvintchouk, M.S., Chief Educational Researcher, Member of ACES. See our detailed commitment to accuracy and quality in our practice tests.

What to expect on the actual SC DMV exam

25

questions

20

correct answers to pass

80%

passing score

List of questions (classic view)

  1. What is the best way to test your vehicle's low air pressure warning signal?
  2. After the initial drop, the maximum acceptable leakage rates per minute are
  3. Under which conditions are front wheel brakes good?
  4. Which of the following is NOT part of the braking process when you're driving a tractor-trailer combination vehicle with an antilock braking system (ABS)?
  5. If the air tanks are not drained,
  6. Which of the following can cause brakes to fade or fail?
  7. Which of the following is NOT part of the air brake system?
  8. When should you use the parking brake?
  9. When should you drain your air tanks?
  10. What is the best way to test if your vehicle's spring brakes come on automatically?
  11. The tractor protection valve
  12. How would you check your truck's slack adjusters?
  13. Why must you pass a knowledge test on air brakes?
  14. An antilock braking system (ABS)
  15. Slack adjusters are
  16. How can you tell if your vehicle is equipped with an antilock braking system (ABS)?
  17. Which of the following are true about a dual air brake system?
  18. Which of the following will be true about your brake function if your antilock braking system (ABS) fails?
  19. Which of the following is NOT part of the drum brake?
  20. How do brakes work on a long, steep downgrade?
  21. The purpose of a supply pressure gauge is
  22. Which of the following should you do before leaving your vehicle unattended?
  23. Which vehicles must have low air pressure warning signals?
  24. At what measurement is the safety valve USUALLY set to open?
  25. Spring brakes are
  26. The low air pressure warning signal will come on before the pressure in the air tanks falls below
  27. A low pressure warning signal is required on
  28. All vehicles equipped with air brakes have
  29. With air brake-equipped vehicles, the parking brakes should be used
  30. The use of air brakes on a downgrade is only a supplement to the
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