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View All Plans- Updated for June 2025
- Based on 2025 SC commercial driver's license manual
Free South Carolina CDL Air Brakes Test 2025
Our South Carolina DMV CDL Air Brakes Practice Tests are the key to passing your Air Brakes knowledge exam on the first attempt. Failure to pass the South Carolina DMV CDL Air Brakes Knowledge Test means that your CDL will include the restriction “L,” prohibiting you from operating commercial motor vehicles (CMVs) with air brakes. Failing the test in South Carolina also results in a one-day waiting period and a fee should you decide to retake the test. This “L” restriction significantly damages your job prospects in this market.
Because most semi-trucks, tractor-trailers, and commercial buses rely on air brakes for safe navigation, removing the air brake restriction from your CDL is vital for expanded job opportunities. South Carolina features a mix of coastal plains, rolling hills, and the Blue Ridge Mountains as well as urban and rural challenges throughout. Interstate highways like I-26 and I-85 feature hilly and flat regions, where air brakes are essential for vehicle control. Weather in the state brings frequent thunderstorms (especially in the summer) and wintry snow and ice. These impact road conditions and require powerful, reliable braking systems, heightening the demand for air brake-qualified drivers. The major transportation routes include I-26 (connecting Charleston to the western part of the state), I-85 (linking South Carolina with Georgia and North Carolina), I-95 (a vital north-south route), and US-301 (used for regional transport).
The Palmetto State demands air brakes in key industries, including manufacturing (automotive and aerospace), agriculture (poultry and cotton), tourism, and logistics. Companies requiring air brake-qualified drivers include BMW (Spartanburg) and Volvo Cars (Charleston) in the manufacturing sector and Mountaire Farms and Perdue Farms in the agriculture industry. XPO Logistics and Old Dominion Freight Line are major logistics companies with fleets of air brake-equipped vehicles. In the charter bus industry, companies like Greyhound Lines, Southeastern Stages, and Carolina Trailways require air brake-qualified drivers, as do the state’s school districts for their full-size buses (employing hundreds of air brake-qualified drivers).
The written Air Brakes knowledge test features multiple-choice questions based on the state’s CDL manual (South Carolina CDL Handbook 2025) and requires a minimum passing score of 80%. Our CDL Air Brakes Practice Tests mimic the official DMV Air Brakes Knowledge Test and cover everything needed to pass it. The instant feedback you’ll receive on all responses will help you learn faster and ensure you pass the knowledge test!
- Perfect for first-time and renewal CDL/CLP applicants, and those adding endorsements
- Triple-checked for accuracy
What you need to know
What to expect on the actual SC DMV exam
questions
correct answers to pass
passing score
List of questions (classic view)
- What is the best way to test your vehicle's low air pressure warning signal?
- After the initial drop, the maximum acceptable leakage rates per minute are
- Under which conditions are front wheel brakes good?
- 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)?
- If the air tanks are not drained,
- Which of the following can cause brakes to fade or fail?
- Which of the following is NOT part of the air brake system?
- When should you use the parking brake?
- When should you drain your air tanks?
- What is the best way to test if your vehicle's spring brakes come on automatically?
- The tractor protection valve
- How would you check your truck's slack adjusters?
- Why must you pass a knowledge test on air brakes?
- An antilock braking system (ABS)
- Slack adjusters are
- How can you tell if your vehicle is equipped with an antilock braking system (ABS)?
- Which of the following are true about a dual air brake system?
- Which of the following will be true about your brake function if your antilock braking system (ABS) fails?
- Which of the following is NOT part of the drum brake?
- How do brakes work on a long, steep downgrade?
- The purpose of a supply pressure gauge is
- Which of the following should you do before leaving your vehicle unattended?
- Which vehicles must have low air pressure warning signals?
- At what measurement is the safety valve USUALLY set to open?
- Spring brakes are
- The low air pressure warning signal will come on before the pressure in the air tanks falls below
- A low pressure warning signal is required on
- All vehicles equipped with air brakes have
- With air brake-equipped vehicles, the parking brakes should be used
- The use of air brakes on a downgrade is only a supplement to the
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