Texas CDL — Air Brakes Practice Test 9

1.Which list correctly names all the parts of total stopping distance for a vehicle with air brakes?

Perception + reaction + brake lag + effective braking distanceReaction + effective braking distance onlyPerception + governor lag + coasting distanceBrake lag + downshift distance + following distance

2.Most heavy-duty vehicles built today use dual air brake systems. What does that mean?

There are two brake pedals, one for each axle groupAir brakes are backed up by a hydraulic master cylinderTwo separate air systems share a single set of brake controlsEach wheel has its own compressor and tank

3.Before starting down a long, steep grade in an air-braked vehicle, when should you shift into the proper low gear?

Halfway down, once speed starts to buildBefore you start down the gradeOnly after the low air warning comes onAt the bottom, to save wear on the transmission

4.Why is it a bad habit to press and release the brake pedal over and over when you don't need to?

It wears out the stop light switch and burns out the brake lightsIt overheats the drums even when you are moving slowlyIt confuses the antilock computer and shuts off ABSIt can bleed off air faster than the compressor replaces it

5.You park an air-braked truck and leave the cab to make a delivery. What does safe practice require you to do first?

Leave the engine running so tank pressure cannot dropApply the parking brakes by pulling the yellow diamond-shaped knob outPush the yellow knob in to lock the spring brakesHold the treadle valve down with a block of wood

6.One half of your dual air brake system suddenly loses pressure on the highway. What should you do?

Stop right away and have the air brake system fixedKeep driving, since the second system makes repairs optionalSwitch the limiting valve to slippery to save airDrain the working tank to equalize the two systems

7.As part of the seven-step air brake check, how do you test that the low pressure warning signal works?

Rev the engine to 2,000 rpm and watch the supply gaugePull the trailer air supply knob and listen for a buzzerShut the engine off, turn the key on, and fan the pedal until the warning activatesOpen a drain valve until the tanks are completely empty

8.During your walk-around you find a brake with an automatic slack adjuster whose push rod stroke is past the legal adjustment limit. What does the handbook recommend?

Readjust it by hand and keep to your normal schedule, since that fixes itLeave it alone, because automatic adjusters correct themselves at the next stopHave it repaired soon, since the long stroke points to a mechanical problemLower the governor cut-out pressure so the push rod travels less

9.You are braking hard in a tractor-trailer where only the tractor has antilock brakes. What should you watch for?

The trailer swinging out; ease off the brakes if it does and you safely canThe tractor's steering wheels locking, since tractor ABS cannot prevent thatThe ABS lamp flashing, which is your signal to pump the pedal rapidlyNothing extra, because the tractor's ABS keeps the trailer from skidding too

10.Your brakes got soaked while you drove through deep water, and the temperature is near freezing. What should you do about the wet brakes?

Set the parking brake hard right away so the wet shoes seat firmly against the drumsDrive in a low gear while lightly applying the brakes so the heat dries themSpray the drums with alcohol from the evaporatorDrain the air tanks twice to pull the water out of the brakes