California CDL — Air Brakes Practice Test 2

1.How thin can brake linings wear before the handbook considers them dangerously thin?

Thinner than 3/4 inchThinner than 1/2 inchThinner than 1 inchThinner than 1/4 inch

2.During an inspection of s-cam brakes with a manual slack adjuster, you pull hard on each slack adjuster (with the parking brakes released and wheels chocked). When does a slack adjuster need adjustment?

If it moves at all when pulled by handIf it moves more than about an inch at the point where the push rod connectsIf it moves more than about three inches where the push rod attachesOnly if the brake drum shows cracks

3.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

4.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

5.Does an anti-lock braking system (ABS) shorten the distance you need to stop?

Yes — it always cuts stopping distance roughly in halfNot necessarily — its benefit is helping you keep control during hard brakingYes — but only on dry pavementNo — it always lengthens stopping distance because it releases the brakes

6.How do you test the service brakes during the final air brake check?

Set the parking brake and pull gently against it in a low gearRoll forward slowly at about 5 mph and press the brake pedal firmly, watching for pulling or a delayed stopPump the pedal with the engine off until the warning buzzer soundsHold the pedal down for one minute and watch the air gauge

7.The safety relief valve on the first air tank opens and releases air. What does that tell you?

The system is working normally and no action is neededThe tanks are full of water and need to be drainedSomething is wrong, and a mechanic should fix the faultThe spring brakes are about to apply automatically

8.Some older vehicles have a front brake limiting valve with "normal" and "slippery" positions. What does the handbook say about using this control?

Switch it to "slippery" whenever the road is wetUse "slippery" only when the vehicle is fully loadedLeave it in the "normal" position, because front-wheel braking is good under all conditionsKeep it in "slippery" at all times to protect the steering axle

9.Your spring brakes are applied. Why should you avoid pushing down on the brake pedal?

It releases the spring brakes and lets the vehicle rollIt empties the air tanks within a few secondsSpring force and air pressure together could damage the brakesIt makes the low air pressure warning come on

10.In stab braking, you let off the brakes when the wheels lock. Why must you hold off until the wheels are rolling again before braking hard a second time?

If you brake again too soon, the vehicle will not straighten outBraking again too soon overheats the brake drumsThe air compressor needs that time to rebuild pressureThe spring brakes need that time to release fully