Ohio CDL — Air Brakes Practice Test 5

1.Why does the manual warn against pressing the brake pedal while the spring brakes are already applied?

It can drain the tanks below the cut-in pressureIt can cause the wig wag to drop into viewIt can lock the parking brake knob in the out positionThe combined force of the springs and air pressure can damage the brakes

2.With the foot brake fully applied and held for one minute on a combination vehicle, what pressure drop is considered too much?

More than 2 psiMore than 4 psiMore than 3 psiMore than 6 psi

3.What is the purpose of an alcohol evaporator in some air brake systems?

To cool the compressor during long climbsTo replace oil lost from the compressorTo reduce ice forming in the air valves in cold weatherTo raise tank pressure above the cut-out level

4.In which situation should you NOT set the parking brakes, using wheel chocks instead?

Whenever the truck is fully loadedAny time you park on a downgradeWhen the brakes are very hot, or very wet in freezing temperaturesWhenever the engine is still running

5.Automatic slack adjusters are found on all vehicles built since what year?

1975199419881998

6.As the compressor fills the tanks, at roughly what pressure does the governor shut the compressor off (the "cut-out" point)?

About 55 psiAbout 125 psiAbout 100 psiAbout 150 psi

7.With air brakes, total stopping distance is made up of four parts. Which set is correct?

Perception, reaction, brake lag, and braking distancePerception, reaction, and braking distance onlyReaction, brake lag, skid, and braking distancePerception, brake fade, brake lag, and braking distance

8.What is the main benefit that antilock brakes (ABS) provide?

They keep the wheels from locking up so you stay in control during hard brakingThey always shorten your stopping distanceThey remove the need for spring brakesThey automatically drain the air tanks

9.On older trucks with a front brake limiting valve control marked "normal" and "slippery," where should the control usually be kept?

In the "slippery" position to prevent skidsHalfway between the two settingsIn the "normal" position, because front-wheel braking is good in all conditionsIn whichever position matches the road temperature

10.How do you test that the parking brake will actually hold the vehicle?

Set it and, in a low gear, ease the truck gently against it to check that it holdsRev the engine to full throttle with the brake setRoll downhill and use only the foot brakeRelease all the air and coast to a stop