Maryland CDL — Air Brakes Practice Test 6

1.When the spring brakes finally set on a lightly loaded rig, or on a slick road surface, what extra danger appears?

The trailer brakes let go before the tractor brakes doThe compressor restarts on its own and rebuilds full pressureThe vehicle can slide and you may lose control of itThe steering axle locks itself into a straight-ahead position

2.When making a normal stop in a truck with a manual transmission, when should you push in the clutch?

Wait until engine speed has dropped near idleThe instant you first touch the brake pedalOnly after the vehicle has completely stoppedHalfway through the stop, at highway rpm

3.When inspecting brake drums, how long a crack is too much?

Any crack of any length is acceptableCracks up to the full width of the friction area are fineA crack running past half of the friction area's widthOnly cracks longer than three inches matter

4.What is the purpose of an alcohol evaporator in an air brake system?

It lowers the chance of ice building up in the valves during cold weatherIt boosts the octane of the fuel supplyIt replaces the need to check tire pressureIt cools the brake drums after long descents

5.What is the function of the stop light switch on an air brake vehicle?

It shuts the engine off if pressure drops too lowIt limits how much air reaches the front brakesIt drains the tanks when you parkIt turns on the brake lights when you apply the brakes

6.What is physically going wrong inside a drum brake when too much heat makes the brakes fade?

The air lines soften and start bleeding pressure out of the chamberThe lining grips less and the drum swells, so the shoes reach farther and push with weaker forceThe slack adjuster tightens up and drags the shoes against the drumThe s-cam turns the wrong way and holds the shoes apart

7.Total stopping distance for an air brake vehicle is made up of which four parts?

Perception, reaction, cornering, and braking distancePerception, reaction, coasting, and braking distanceReaction, braking, skidding, and rolling distancePerception, reaction, brake lag, and braking distance

8.When checking a slack adjuster on an s-cam brake, how much movement means it should be inspected for proper adjustment?

More than about a quarter inchAny movement at allMore than about three inchesMore than about one inch

9.If you keep driving after the low air pressure warning comes on and the spring brakes finally apply, why can a heavily loaded vehicle take a long distance to stop?

Because the service brakes apply at double strengthBecause the ABS shuts off all brakingBecause the trailer brakes release automaticallyBecause the spring brakes don't act on every axle

10.At about what pressure does the governor normally stop the compressor from pumping (the cut-out point)?

Around 55 psiAround 80 psiAround 100 psiAround 125 psi