California CDL — Air Brakes Practice Test 9

1.Why is it a bad habit to press and release the brake pedal over and over when you do not need to?

It makes the governor cut out the compressor too earlyIt causes the safety relief valve to openIt sends extra air to the spring brakes and locks them onEach release vents air, and you can use it up faster than the compressor refills the tanks

2.How do brakes that are out of adjustment contribute to brake fade on the rest of the vehicle?

They stop doing their share of the work, so the other brakes overheatThey grip harder than the others and lock their wheelsThey leak air and trigger the low pressure warningThey cause the governor to cut out the compressor

3.During an inspection of s-cam brakes with a manual slack adjuster, you pull hard on each slack adjuster (with the parking brakes released and wheels chocked). When does a slack adjuster need adjustment?

If it moves at all when pulled by handIf it moves more than about an inch at the point where the push rod connectsIf it moves more than about three inches where the push rod attachesOnly if the brake drum shows cracks

4.You must make a quick emergency stop in a vehicle without anti-lock brakes. Which describes the stab braking method?

Apply light, steady pressure and steer sharply around the hazardApply the parking brake in short bursts while steering straightApply the brakes fully, release when the wheels lock, and reapply when they start rolling againPump the pedal rapidly several times per second until stopped

5.In the applied leakage test, you shut off the engine, release the parking brake, and hold the foot brake fully down for one minute. On a single vehicle, what is the most the air pressure may drop?

1 psi2 psi3 psi6 psi

6.The safety relief valve on the first air tank opens and releases air. What does that tell you?

The system is working normally and no action is neededThe tanks are full of water and need to be drainedSomething is wrong, and a mechanic should fix the faultThe spring brakes are about to apply automatically

7.Your CDL skills test vehicle has air-over-hydraulic brakes instead of a full air brake system. What restriction will be placed on your CDL?

No restriction — air-over-hydraulic counts as full air brakesA restriction against towing any trailerA restriction limiting you to vehicles under 26,001 poundsA restriction against driving vehicles equipped with a full air brake system

8.Which type of foundation brake is found at the wheels of most heavy vehicles that use air brakes?

S-cam drum brakesAir-over-hydraulic disc brakesWedge brakesElectric drum brakes

9.Who needs to study the Air Brakes section and pass the air brakes knowledge test in California?

Only Class A applicants pulling double trailersOnly drivers of vehicles over 40 feet longAny driver who wants to operate a vehicle equipped with air brakes, regardless of classOnly drivers transporting hazardous materials

10.On heavy trucks and buses, the parking and emergency brakes are held on by mechanical force — usually springs — rather than by air. Why?

Air pressure applies the brakes too slowly for parkingCompressed air freezes whenever the engine is shut offAir pressure can leak away over timeSprings produce more stopping power than the service brakes