Arkansas CDL — Air Brakes Practice Test 9

1.You press the brake pedal to slow for a red light in an air-braked truck. Which of its three braking systems is doing that work?

The parking brake systemThe emergency brake systemThe service brake systemThe spring brake reserve system

2.Where is the safety relief valve installed in an air brake system?

On each brake chamber at the wheelsOn the dash, next to the parking brake knobIn the first tank that the compressor pumps air intoOn the last tank before the trailer air lines

3.Outside of an emergency, when should automatic slack adjusters normally need to be adjusted by hand?

At every pre-trip inspectionWhenever the brakes feel softOnly during brake maintenance and when the adjusters are being installedOnce a week, at the end of the last driving day

4.Partway through a trip, your air compressor quits. What can you still count on from the air already stored in the tanks?

Normal braking for the rest of the trip, since the tanks refill themselvesEnough air to use the brakes several timesNothing at all, because the brakes fail the moment the compressor stopsEnough air to keep the spring brakes released for as long as you need

5.During the walk-around, which brake lining condition is acceptable?

Firmly attached, free of oil and grease, and not worn thinLoose on the shoeSoaked with greaseWorn dangerously thin

6.On a long downgrade in the right low gear, how firmly should you apply the brakes each time your speed reaches the safe speed?

Just firmly enough to feel a definite slowdownAs hard as possible to stop quicklyBarely touching the pedal so the brakes never warm upHard enough to lock the wheels briefly

7.What is the job of the air compressor governor?

It limits how fast the truck can go on air brakesIt releases air if tank pressure gets too highIt warns you when air pressure is lowIt controls when the compressor pumps air into the storage tanks

8.You keep driving after the low air warning comes on, and tank pressure keeps dropping. On a typical tractor or straight truck, around what pressure will the spring brakes come fully on?

Around 55 psi, the moment the warning comes onAround 80 to 85 psiOnly at 0 psi, once the tanks are emptyTypically between 20 and 30 psi

9.According to the manual, what decides how much heat a brake drum can absorb before it is damaged?

How hard and for how long the brakes are usedOnly the outside air temperatureThe tire pressure on that wheelWhether the vehicle has a dual air system

10.On an air-braked vehicle with drum brakes, how are the wheels and brake drums arranged?

The drums are at each end of the axles, and the wheels are bolted to themThe drums sit in the cab and connect to the wheels by cablesEach drum is mounted on the driveshaft, away from the wheelsOnly the front axle has drums; the rear wheels rely on the spring brakes alone