Michigan CDL — Air Brakes Practice Test 6

1.On a truck that has a dual air brake system, how much pressure should the compressor build in both halves before you drive off?

60 psi85 psi125 psi100 psi

2.How does an air brake vehicle switch on its brake lights to warn drivers behind it?

A cable pulled by the slack adjusterA mechanical arm similar to the wig wagAn electric switch triggered by air pressure when you apply the brakesThe governor closing at cut-out pressure

3.On newer air brake vehicles, what does the parking brake control usually look like?

A round blue push buttonA yellow, diamond-shaped push-pull knobA red octagonal leverA green sliding switch

4.A tank fitted with a manually operated drain valve should be emptied how often?

Only when the automatic drain failsRoughly once a weekEvery time the compressor cuts outBy the driver once each day's driving is finished

5.During inspection, a brake drum or disc must not have a crack longer than what?

Half the width of the friction areaOne quarter inchThe full width of the friction areaTwo inches

6.Why do most heavy-duty vehicles use a dual air brake system?

To do away with the need for spring brakesFor safety, since it gives two separate air brake systems that share one set of controlsTo reduce the number of air tanks requiredTo allow braking even without a compressor

7.Which statement best describes what antilock brakes actually do for you?

They shorten your stopping distance on every surfaceThey replace the need for a service brake systemThey let you drive faster on iceThey keep the wheels from locking during hard braking so you stay in control, though they may not shorten stopping distance

8.If one half of a dual air brake system loses most of its pressure, what happens?

Either the front or the rear brakes won't work fully, so stopping takes longerThe parking brake releases automaticallyBraking is unaffected because the halves are identicalThe compressor shuts down permanently

9.What is the job of an alcohol evaporator in an air brake system?

To cut the chance of ice forming in the brake valves during cold weatherTo push tank pressure above 150 psiTo replace the water drained from the tanksTo keep the compressor drive belt from slipping

10.Which sequence correctly describes stab braking?

Apply light steady pressure and never releaseUse the parking brake in short burstsPress the brakes fully, release when the wheels lock, then reapply fully once the wheels roll againCut air to the front brakes, then brake hard