- A 2/32 inch in every major groove
- B 1/32 inch on the steer tires only
- C At least 4/32 inch in every major groove Correct answer
- D 6/32 inch on at least one tire
Why this is the correct answer
Federal regulation requires at least 4/32 inch of tread depth on steer tires; 2/32 inch on other tires.
How this topic appears on the test
The General Knowledge CDL exam covers Vehicle inspection as a recurring theme. Test-writers favor questions that probe whether the applicant has internalized the safe operating procedure, not merely memorized the rule. When you encounter a question on this topic, slow down and verify that the answer you've chosen describes what a careful, defensive driver would actually do — not what is technically permissible.
If you missed this question, that's exactly the right outcome of a practice session: the goal is to surface gaps before the actual test. Open your state CDL manual to the Vehicle inspection section and re-read the relevant subchapter. Then come back and run through the rest of the General Knowledge practice exam.
For drivers preparing for the General Knowledge CDL exam, additional context — including federal manual excerpts, employer hiring practices, and DOT medical guidance — is widely available from industry resources. Continue reading on a recommended industry resource for further detail. Always cross-check anything you read with the current edition of your state CDL manual, since enforcement guidance is updated periodically.