Wisconsin CDL — Air Brakes Practice Test 3

1.What is the purpose of a modulating control valve for the spring brakes?

To drain the tanks slowly at day's endTo keep the front brakes from locking on iceTo warn the driver before the tanks run emptyTo let you apply the spring brakes gradually if the service brakes fail

2.Which sequence describes the stab braking method?

Press lightly and hold steady until the vehicle stopsPump the pedal quickly the whole way down the roadApply partway, then ease off little by littleApply fully, release when the wheels lock, then reapply fully once they roll again

3.When you pull hard on an S-cam slack adjuster, about how much movement suggests it needs adjustment?

Any movement at allMore than roughly one inch where the push rod connectsMore than three inchesMore than half the width of the wheel

4.What does an alcohol evaporator do for an air brake system?

It filters oil out of the compressed airIt raises the boiling point of the brake fluidIt reduces the risk of ice forming in the brake valves in cold weatherIt removes the need to drain the tanks each day

5.Using the proper braking technique on a downgrade, when do you release the brakes?

As soon as you feel any slowdown at allOnly at the very bottom of the gradeOnce your speed is about 5 mph below your safe speedWhen the drums begin to smoke

6.What does a supply pressure gauge tell the driver?

How much pressure is going to the brakes at that instantHow much air pressure is being held in the tanksWhether the parking brakes are setThe temperature of the brake drums

7.If you keep driving after the low air warning comes on, what limits your braking?

The parking brake locks the steering wheelControlled braking works only while air remains, and the spring brakes set at 20 to 45 psiThe compressor overheats and quitsThe stop lamps stop working first

8.Your dual air system takes far too long to build pressure during the pre-trip check. What is the danger if you drive it anyway?

Tank pressure can fall too low while you are driving and force an emergency stopThe governor will begin cutting in far below its normal settingThe alcohol evaporator will flood the tanks with fluidThe ABS lamp will stay lit until the tanks are drained

9.During inspection, a cracked brake drum is considered unsafe when the crack is longer than what?

One inchThe entire width of the friction surfaceMore than half of how wide the friction surface isOne-quarter inch

10.What is 'brake lag' in an air brake system?

The half-second or more it takes air to reach and work the brakesThe delay before the compressor cuts inThe time a driver needs to notice a hazardThe gap between setting and releasing the parking brake