Mississippi CDL — Air Brakes Practice Test 1

11.During controlled braking in an emergency, how should you handle the steering wheel while the brakes are applied?

Turn sharply to steer around the hazardLet go of the wheel until the vehicle stopsKeep steering movements very smallRock the wheel back and forth to keep the tires rolling

12.Some pre-1975 trucks carry a front brake limiting valve worked from the cab. What was it meant to do, and what is the catch?

It was meant to reduce front-wheel skids on slick roads, but it actually reduces stopping powerIt was meant to cool the front brakes, but it wears out the liningsIt was meant to add front braking on ice, but it locks the rear wheelsIt was meant to replace ABS, but it works only above 55 mph

13.A bus has lost its main air pressure, and you are holding in the spring-loaded button of its dual parking control valves to move it. What happens when you let go?

The bus keeps rolling until the separate tank refillsThe service brakes lock upThe low air warning shuts offThe spring brakes come back on

14.In a dual air brake system, when should the low air warning light and buzzer shut off after start-up?

As soon as either system passes 20 psiWhen pressure in both systems rises to the manufacturer's set value, which must be above 55 psiWhen you release the parking brakeAfter the engine has run for 45 seconds

15.A mechanic says the air disc brakes on your truck work like a big c-clamp. Which part, turned by the slack adjuster, does the clamping?

A wedgeAn S-shaped camA modulating control valveA power screw

16.Your truck has air tanks larger than the minimum size, and building from 85 to 100 psi takes a bit longer than 45 seconds. What does the manual say?

A longer buildup can still be safe; check the manufacturer's specificationsIt is always a defect that must be repaired before drivingLarger tanks should fill faster than 45 secondsRemove the extra tanks to meet the time limit

17.During your walk-around, you spot a crack in a brake drum. When is the crack too long?

Only when it goes all the way through the drumWhen it is longer than one inchWhen it is longer than the brake lining is thickWhen it is longer than half the width of the friction area

18.Your truck has an alcohol evaporator, and you keep it filled every cold day. Does that let you skip draining the air tanks?

Yes, because the alcohol absorbs all of the water and oilYes, but only during the summer monthsNo; the tanks still need daily draining to remove water and oil unless they drain automaticallyNo, but draining once a week is enough

19.You find you need more and more application pressure to hold the same speed. Besides fading brakes, what else can cause this?

Tank pressure above the governor's cut-out levelA full alcohol evaporatorHaving ABS on the trailer onlyPoorly adjusted brakes, leaking air, or a mechanical fault

20.Your dual air brake truck has only one supply pressure gauge in the cab. How can that one gauge show both halves of the system?

It switches between the two systems every few secondsIt shows only the primary system, since the secondary needs no gaugeIt has two needles, one for each systemIt shows the average of the two systems