CDL Air Brakes Practice Test
If you skip the air brakes knowledge test, your CDL gets an L restriction: no air-brake vehicles, which rules out most trucking jobs. This practice test hits the numbers people forget on test day: governor pressures, low-air warnings, spring brake ranges, and leak rates. Study your state's manual; the figures below follow the standard CDL manual.
Use this test the right way
Every question you miss is a pointer to a manual section, not just a wrong answer. The explanations here tell you why, but your state's manual is what the real test is written from, and a few numbers and rules genuinely vary by state.
When your practice scores are steady, book the real test through your state and bring the documents they list. Passing the knowledge test gets you the learner's permit; the required entry-level training (ELDT) and the skills test still follow for most paths.
FAQ
Is this the actual CDL test?
No. The real knowledge test is administered by your state and built from your state's commercial driver manual. This is a free study tool covering the standard manual topics.
How many questions are on the real test?
It varies by state, but the general knowledge test is commonly around 50 questions with an 80 percent passing score. Check your state's CDL page for specifics.
What happens if I fail the real knowledge test?
You can retake it, but most states charge a retest fee and some make you wait. The retest line is where skipping the manual gets expensive.