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  • Updated for March 2025
  • Based on 2025 OK commercial driver's license manual

Free Oklahoma CDL Air Brakes Test 2025

Securing a CDL without an air brake restriction is vital for expanded job opportunities in Oklahoma because most semi-trucks and tractor-trailers rely on air brakes for safe navigation. Without passing the Oklahoma SOK CDL Air Brakes Knowledge Test, your CDL will include the restriction “L,” preventing you from operating commercial motor vehicles (CMVs) with air brakes. Failing the air brakes test in Oklahoma results in a one-day waiting period and a retest fee should you decide to retake the test. Our Oklahoma SOK CDL Air Brakes Practice Tests help you pass your knowledge exam on the first attempt.

Due to Oklahoma’s diverse terrain, from the Flat Plains (and high winds) to the steep grades along the mountainous regions (Arbuckle and Wichita Mountains), mastering air brakes is essential. Additionally, winter brings ice storms and heavy rains, and these hazardous conditions require precise braking and air brake-qualified drivers. The major transportation routes I-40 (critical east-west route), I-35 (key north-south freight corridor), I-44 (including the Turner and Will Rogers Turnpikes), and Route 69 (freight transport into eastern Oklahoma) are the lifeblood of the state. As most semi-trucks and tractor-trailers rely on air brakes, restriction “L” would severely limit your job opportunities.

The Sooner State relies on drivers with the air brake qualification in key industries including energy, agriculture, and manufacturing. Major companies requiring this qualification include Chesapeake Energy, Devon Energy, and ONEOK in the energy sector and Oklahoma Ag Transports and K&J Transports in agriculture. Ditch Witch and Kimberly-Clark are major companies in the manufacturing sector requiring air brake-qualified drivers. Additionally, Village Tours and Jefferson Lines require them in the charter bus industry. Oklahoma also has thousands of full-size school buses that require air brake-qualified drivers. The “L” restriction makes the above-listed jobs unattainable.

Our CDL Air Brakes Practice Tests cover all essential knowledge for the official SOK Air Brakes Knowledge Test. The information you learn will also be useful as you practice inspecting and operating CMVs to pass your skills test. The written Air Brakes knowledge test features multiple-choice questions based on the state’s CDL manual (Oklahoma CDL Handbook 2025) and requires a score of at least 80% to pass.

Our Practice Tests mimic the official knowledge test and offer real-time feedback on all responses. This scientifically proven approach helps you learn faster and ensures you pass the test.

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

What you need to know

4.71 out of 5 • 14 votes
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 OK SOK exam

25

questions

20

correct answers to pass

80%

passing score

List of questions (classic view)

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