South Dakota CDL Air Brakes Practice Test (SD) 2

5 out of 5 (37 votes)
80% Passing score
20 Questions
4 Mistakes allowed
Preparing for your CDL air brakes endorsement in South Dakota is crucial, especially considering our unique driving conditions. The South Dakota CDL air brakes practice test is a comprehensive tool designed to help you master the necessary knowledge and skills. With 20 multiple-choice questions, this practice test covers essential topics such as components, operation, safety inspections, and stopping distance calculations. You'll find questions on dual air brake systems, which are vital for maintaining safety on our rural and often isolated highways. Updated for 2026, our SD DMV practice test ensures that you are studying the most current driving laws and regulations. This regular update is critical because staying informed about the latest changes can make a significant difference in your preparedness for the CDL test. The DMV driving test practice we offer is designed to complement any drivers education program or ELDT course you might be taking. While it doesn't replace state-certified education, it serves as an excellent supplementary tool to reinforce your learning. One of the standout features of our South Dakota CDL air brake practice test is the variety of questions. Drawing from a large pool of permit test questions and answers, the South Dakota practice permit test offers a broad spectrum of scenarios and information, thoroughly preparing you for the actual DMV written test. This extensive coverage is particularly useful given the diverse driving conditions in SD, from the vast open plains to the Black Hills' winding roads. South Dakota's local culture and environment play a significant role in shaping driving practices. For instance, understanding how to handle long distances without frequent stops and managing air brakes effectively in varying weather conditions are vital skills for any commercial driver in the state. Our South Dakota CDL air brakes practice test helps you gain these insights, ensuring that you are well-prepared not just for the test, but for real-world driving in SD. By scoring at least 16 out of 20 questions correctly, you can confidently move forward in your CDL journey. This South Dakota DMV air brake test is your key to achieving a successful outcome on your air brakes CDL test, providing you with the knowledge and confidence needed to excel.
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Sample South Dakota Air Brakes Test Questions

Question 1

On a newer air-brake vehicle, which color identifies the diamond-shaped parking-brake control?

  1. A Red
  2. B Green
  3. C Yellow
  4. D Pink

Correct answer: C – Yellow

The South Dakota Commercial Driver License Manual identifies the newer parking-brake control as a yellow, diamond-shaped push-pull knob. Pulling it out applies the spring brakes, and pushing it in releases them. The red, eight-sided knob is used for the trailer air supply.

Source: South Dakota Commercial Driver License Manual — § 5.1.15, “Parking Brake Controls”

Question 2

If a vehicle has no automatic air-tank drains, draining the tanks once each week is sufficient. True or false?

  1. A True
  2. B False

Correct answer: B – False

The South Dakota Commercial Driver License Manual directs drivers to drain air tanks at the end of each working day when automatic drains are not installed. Draining removes moisture and oil that collect in the system. Allowing these contaminants to accumulate can contribute to brake failure.

Source: South Dakota Commercial Driver License Manual — § 5.4.8, “Parking Brakes”

Question 3

During an applied air-leakage test, a combination vehicle may lose no more than one psi in one minute. True or false?

  1. A True
  2. B False

Correct answer: B – False

For the applied leakage test described in the South Dakota manual, fully apply the foot brake and wait for the initial pressure drop to stabilize. Hold the brake for one minute. A combination vehicle must not lose more than four psi during that minute; three psi is the limit for a single vehicle.

Source: South Dakota Commercial Driver License Manual — § 11.1.2, “Air Brake Check (Air Brake Equipped Vehicles Only)”

Question 4

On a long, steep downgrade, service brakes should supplement the engine’s braking effect after the proper low gear is selected. True or false?

  1. A True
  2. B False

Correct answer: A – True

Before descending, select a low gear that allows engine braking to control most of the vehicle’s speed. Use the service brakes only as a supplement, applying them firmly enough to produce a definite slowdown and then releasing them. Excessive service-brake use can create heat and cause brake fade.

Source: South Dakota Commercial Driver License Manual — § 5.4.6, “Proper Braking Technique”

Question 5

Why should you avoid repeatedly fanning the service brakes to control speed on a long downgrade?

  1. A It reduces the amount of air the brakes use
  2. B It keeps the brake linings cool
  3. C It can overheat the brakes and cause brake fade
  4. D It increases the engine’s braking power

Correct answer: C – It can overheat the brakes and cause brake fade

Repeated use of the service brakes can produce excessive heat, reducing friction and causing brake fade. Each unnecessary application and release also exhausts compressed air from the system. On a downgrade, select the proper low gear and use the recommended controlled braking technique rather than continuously fanning the pedal.

Source: South Dakota Commercial Driver License Manual — § 5.1.7, “The Brake Pedal”, South Dakota Commercial Driver License Manual — § 5.4.5, “Brake Fading or Failure”

Question 6

What is the main function of automatic slack adjusters?

  1. A Regulate pressure inside the air tanks
  2. B Apply the spring brakes when parked
  3. C Change the amount of free play in the brake pedal
  4. D Keep the foundation brakes properly adjusted

Correct answer: D – Keep the foundation brakes properly adjusted

Automatic slack adjusters maintain brake adjustment and adjust themselves during full brake applications. They must still be inspected because excessive movement can indicate an adjustment or mechanical problem. If a reachable slack adjuster moves more than about one inch where the pushrod attaches, the brakes may need service.

Source: South Dakota Commercial Driver License Manual — § 5.3.2, “During Step 5 Walk-around Inspection”

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