South Carolina CDL Permit Test - Air Brakes

Number of questions: 25
Passing score: 20
Directions: This endorsement is required for driving a vehicle with air brakes. To receive this endorsement, applicants must pass a written test. The test consists of 25 multiple choice questions. Each question has two, three or four answer choices. To pass, the applicant must answer at least 20 questions correctly. Test questions come from the South Carolina Commercial Driver License Manual. Questions come from the chapter covering: Air Brakes. The Air Brakes endorsement may be used with the Class A, B or C CDL.
You have made error so far
Passing grade —
5 or fewer errors
Truck tractors with air brakes built after March 1, 1997, have:
An extra set of brakes
Voice-activated brakes
Cruise control
Using the brakes creates heat. What happens if there is too much heat produced?
The brakes may not work
The brakes may squeak more than usual
The brakes will likely brake unevenly
What can happen if the parking brakes are used in very wet weather?
The brakes will squeak
The brakes may freeze so the vehicle cannot move
The brakes may suddenly release by themselves
The brakes may become too smooth
Air tank drains:
Allow rain water to enter the tank
Are used to drain water and oil from the air tank
Should never be opened
Must remain open while driving
Brakes can get out of adjustment:
If they are hot
In the winter time
If they are used
If brakes on one side are used more often than the other side
What is brake lag?
The time required for the brakes to work after the brake pedal is pushed
The distance from the brake pedal’s resting position to the floor
The amount of air pressure used to stop the vehicle
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