California CDL — Air Brakes Practice Test 6

11.You take your CDL skills (drive) test in a vehicle that is not equipped with air brakes. What happens to your license?

Nothing — air brakes only matter for the knowledge testYour CDL is issued with an air brake restrictionYou must retake the entire CDL program within 30 daysYou are limited to intrastate driving only

12.It is freezing outside and your brakes are very wet. Before you park, what does the handbook suggest doing about the wet brakes?

Drag the brakes gently in a low gear so the heat dries them outSet the parking brakes right away so the linings cannot freezeFan the brake pedal with the engine off to blow the water outDrain the air tanks to remove the water from the brake drums

13.During the air brake check, how do you test the low pressure warning signal?

Drive at low speed and apply the parking brake to see if the light flickersRev the engine to operating rpm and watch for the warning at cut-out pressureOpen a drain valve slightly and listen for the buzzer at 100 psiFan down air pressure with the brake pedal, key on and engine off, until the warning comes on before 55 psi

14.Your straight truck has working anti-lock brakes on every axle, and it is the only kind of vehicle you drive. How may you brake in an emergency stop?

You must use stab braking, releasing each time the wheels lockYou should brake lightly and steer onto the shoulder insteadYou should pull the parking brake knob to add the spring brakesYou can apply the brakes fully

15.The air compressor governor controls when the compressor pumps air into the storage tanks. At about what pressure does the governor stop the compressor from pumping (the "cut-out" pressure)?

About 60 psiAbout 100 psiAbout 125 psiAbout 150 psi

16.Dual air brake systems are used on most heavy-duty vehicles. What safety advantage does a dual system give you?

It doubles the vehicle's braking power on steep downgradesIt lets the compressor rest while one system is in useIt allows the trailer and tractor to brake at different ratesBecause the two systems are separate, losing air in one still leaves the brakes on the other system working

17.What does the supply pressure gauge on the dashboard tell you?

How much pressure you are applying to the brakesHow much air pressure is in the air tanksHow fast the compressor is pumpingHow much the brakes have worn since the last adjustment

18.When air pressure falls far enough, the spring brakes on tractors and straight trucks come fully on. In what range does that happen?

55 to 75 psi20 to 45 psi85 to 100 psi5 to 10 psi

19.Air brakes are really three braking systems in one. Which of them stops the vehicle if the brake system fails, using parts of the other two?

The service brake systemThe emergency brake systemThe parking brake systemThe anti-lock braking system

20.Some buses have a second control valve, fed by its own air tank, that releases the spring brakes after main air pressure is lost. Why must you plan carefully before using it to move the bus?

Using it permanently disables the spring brakesIt works only while the engine is shut offIt releases the brakes on the front axle onlyIts tank holds only enough air to release the brakes a few times