CDL Knowledge Test
CDL Practice Test Questions by Subtest, with Answers
Free CDL Class A practice questions with answers and explanations, covering General Knowledge, Air Brakes, Combination Vehicles and every endorsement.
1443 questions
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During a pre-trip inspection, you find a tire with a large bulge in the sidewall. What should you do?
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Correct answer to question 1 (General Knowledge): Take the vehicle out of service until the tire is replaced
Why
A bulge means the tire's internal structure is damaged and it can fail without warning, including a blowout at speed. It must be replaced before the vehicle goes back into service, not just monitored or reinflated.
How to study here
About the CDL knowledge test
The CDL Class A knowledge tests follow the federal FMCSA standard: General Knowledge runs 50 questions and you need 80% to pass. Air Brakes, Combination Vehicles and each endorsement are tested separately.
1443 practice questions cover General Knowledge, Air Brakes, Combination Vehicles and the Tanker, HazMat, Doubles and Triples, Passenger and School Bus endorsements, each with an explanation.
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Sample questions
- During a pre-trip inspection, you find a tire with a large bulge in the sidewall. What should you do?
- Why is backing slowly considered safer than backing at a normal driving speed?
- Why should you check your mirrors before, during, and after changing lanes, not just once beforehand?
- What is the function of the supply (wet) tank in an air brake system?
- Why is following distance especially important when driving a combination vehicle in heavy traffic?
- Why is the low air pressure warning test still relevant to check even in a multi-trailer combination with several tanks contributing to overall system air?
- You are asked to sign for a hazmat shipment without reviewing the shipping papers first. What should you do?
- You smell alcohol on a passenger who is causing a disturbance. What is the appropriate response?
- Why should a driver be aware of a vehicle's designated maximum speed for passenger operation, which may be lower than the vehicle's overall mechanical top speed?
Practice 1440+ CDL Class A questions free in the app, with explanations and state exam formats.