South Dakota CDL Air Brake Test (SD) 2026

5 out of 5 (40 votes)
80% Passing score
20 Questions
4 Mistakes allowed
If you're gearing up for your commercial driver's license, our South Dakota CDL air brakes practice test is the reliable study tool you need. This SD CDL air brakes practice test offers a comprehensive mix of 20 multiple-choice questions covering every aspect of air brake systems. Delve into the crucial components such as compressors, reservoirs, and brake chambers, along with the operational principles and safety protocols necessary for mastering the system. Understanding the unique brake lag time inherent to air brakes is essential for calculating accurate stopping distances, and our questions ensure you're well-prepared to handle this. Achieving a passing score on this CDL air brake test requires correctly answering at least 16 out of the 20 questions, ensuring you're thoroughly prepared for the real test. We believe in providing reliable study tools rather than shortcuts or so-called 'DMV test cheat sheets' that might promise all the answers. Such materials often lack authenticity and legality, posing risks and costs without guaranteed success. Our South Dakota practice permit test, on the other hand, is lawful and proven effective, giving you the confidence and knowledge needed to excel. Our South Dakota DMV air brake test also includes several study aids to enhance your learning experience. If you encounter a challenging question, you can request a hint to guide you towards the correct answer. Additionally, if you answer a question incorrectly, a detailed explanation of the correct answer will be provided, reinforcing your understanding and helping you avoid similar mistakes in the future. We offer a wide variety of questions to ensure a thorough preparation for the DMV written test. Our extensive pool of permit test questions and answers guarantees that you get ample opportunity to learn and understand every concept related to air brake systems. Trust our SD CDL air brake practice test to provide a solid foundation for your commercial driving career, ensuring safe and effective air brake operation.
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Sample South Dakota Air Brakes Test Questions

Question 1

At 55 mph on dry pavement, air-brake lag adds approximately 32 feet to stopping distance.

  1. A TRUE
  2. B FALSE

Correct answer: A – TRUE

In the South Dakota CDL manual’s example, air-brake lag at 55 mph adds about 32 feet to the stopping distance. Brake lag is the delay between pressing the pedal and the brakes beginning to work. Under good traction and brake conditions, the example’s total stopping distance is more than 450 feet.

Source: South Dakota Commercial Driver License Manual — § 5.4.4, “Stopping Distance”

Question 2

Front-wheel brakes should provide normal braking under all road conditions.

  1. A TRUE
  2. B FALSE

Correct answer: A – TRUE

The CDL manual teaches that front-wheel braking is effective under all conditions and that braking-related front-wheel skids are unlikely even on ice. If an older vehicle has a manually controlled front-brake limiting valve, keep it in the normal position. The slippery setting reduces front-brake pressure and overall stopping power.

Source: South Dakota Commercial Driver License Manual — § 5.1.13, “Front Brake Limiting Valve”

Question 3

During an applied air-leakage test on a combination vehicle, what is the maximum acceptable pressure loss in one minute?

  1. A 2 psi
  2. B 3 psi
  3. C 4 psi
  4. D 5 psi

Correct answer: C – 4 psi

Build the system to governor cutout pressure, shut off the engine, release the parking brakes and tractor-protection valve, and fully apply the foot brake for one minute. A combination vehicle may lose no more than four psi during that time. A greater pressure drop indicates excessive leakage that must be repaired before driving.

Source: South Dakota Commercial Driver License Manual — § 5.3.3, “Step 7 Final Air Brake Check”

Question 4

A supply-pressure gauge shows how much air pressure is in the vehicle’s air tanks.

  1. A TRUE
  2. B FALSE

Correct answer: A – TRUE

The supply-pressure gauge displays the amount of pressure in the air tanks. A dual air-brake system may use a separate gauge for each half of the system or one gauge with two needles. It does not measure or time the movement of an S-cam.

Source: South Dakota Commercial Driver License Manual — § 5.1.9, “Supply Pressure Gauges”

Question 5

What should you do when the low-air-pressure warning first activates while driving?

  1. A Stop safely as soon as possible
  2. B Continue to the next scheduled service stop
  3. C Disable the warning to avoid distraction
  4. D Repeatedly pump the brakes to silence it

Correct answer: A – Stop safely as soon as possible

Bring the vehicle to a safe stop immediately while enough air remains to control the brakes. Do not wait for the spring brakes to apply automatically, because control may become difficult as pressure continues dropping. Repeatedly pumping or fanning the brakes consumes more air and worsens the condition.

Source: South Dakota Commercial Driver License Manual — § 5.1.14, “Spring Brakes”

Question 6

In the standard low-air warning test, the warning must activate before tank pressure falls below what level?

  1. A 80 psi
  2. B 70 psi
  3. C 55 psi
  4. D 40 psi

Correct answer: C – 55 psi

The current South Dakota CDL manual requires the warning to activate before tank pressure falls below 55 psi. In a dual system, watch the tank with the lowest pressure. The manual notes that an older vehicle may use one-half of the compressor governor cutout pressure and that large buses commonly provide an earlier warning.

Source: South Dakota Commercial Driver License Manual — §§ 5.1.11 and 5.3.3, “Low Air Pressure Warning” and “Step 7 Final Air Brake Check”

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