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North Carolina CDL — Air Brakes Practice Test 1

The North Carolina CDL — Air Brakes knowledge test has ~25 questions; you need ~20 correct (80%) to pass.

This practice test follows that format: 25 questions, pass with 20 correct. Answer every page, then grade it to see the answers and explanations.

Questions 1–10 of 25

  1. 1.Why is it important to drain the air storage tanks?
  2. 2.On a tractor or straight truck, the spring brakes come fully on when air pressure falls into roughly what range?
  3. 3.What is the purpose of a modulating control valve?
  4. 4.How should you test the service brakes at the end of the brake check?
  5. 5.Total stopping distance for an air-brake vehicle is made up of which four parts?
  6. 6.On a vehicle with an application pressure gauge, needing steadily more pressure to hold the same speed is a sign of what?
  7. 7.What is a 'wig wag' device?
  8. 8.Which type of foundation brake is the most common on air-brake vehicles?
  9. 9.At about what tank pressure does the governor normally reach its 'cut-out' point and stop the compressor?
  10. 10.What happens if a major leak lets all the air out of the brake system?

0 of 25 answered