Tennessee CDL — Air Brakes Practice Test 4

11.Does ABS guarantee a shorter stopping distance?

Yes; it always cuts stopping distance roughly in halfYes; it stops the vehicle instantly with no lagNo; it actually makes every stop longerNo; its main value is keeping the vehicle under control during hard braking

12.What is a "wig wag" low air pressure warning device?

A mechanical arm that drops into view when pressure drops below 55 psiA gauge that counts the seconds of pressure buildupA valve that vents excess pressure at 150 psiA knob you pull to set the parking brakes

13.How do you test that the parking brake will hold?

Rev the engine to full throttle in neutralSet it, then in a low gear gently try to ease forward against itRoll downhill and release it suddenlyPump the brake pedal ten times quickly

14.On a newer air brake vehicle, how do you set the parking brakes?

Push in the yellow diamond-shaped knobPull out the yellow diamond-shaped knobHold the brake pedal down and set a leverTurn the ignition key one notch back

15.What does a supply pressure gauge tell the driver?

How far the brake shoes have wornHow much pressure you are sending to the brakesHow much pressure is stored in the air tanksHow hot the brake drums have become

16.On a long, steep downgrade, the braking effect of the service brakes should be treated as what?

The only thing you need to control speedOnly a supplement to the engine's braking effectA replacement for gearing downSomething to avoid using entirely on hills

17.What causes brake fade from overheating?

Water freezing inside the brake chambersThe governor cutting out too earlyToo much heat changing the lining and expanding the drumsThe alcohol evaporator overfilling the system

18.Why are spring brakes held off by air pressure while you drive rather than held on by air?

Because springs are cheaper than air tanksBecause the governor cannot supply air when parkedBecause air pressure can leak away, so mechanical force must hold the brakes onBecause the compressor only runs while moving

19.If one side of a dual air system loses most of its pressure, what happens to your stopping?

Nothing changes; the other system covers all brakesIt takes longer to stop because some brakes are not working fullyThe vehicle stops faster than normalThe parking brakes take over automatically at speed

20.How do you test the service brakes as part of the final check?

Roll ahead at roughly five mph, then press the brakes hard, noting any pulling or delayBrake hard from highway speed to lock the wheelsHold the pedal down for a full minute while parkedCoast in neutral without touching the pedal