Missouri CDL — Air Brakes Practice Test 6

1.What do air brakes depend on to operate the brakes?

Hydraulic fluid held under pressureCompressed air moving through the systemElectric current sent to each wheelEngine vacuum stored in a reservoir

2.If a system includes an alcohol evaporator, can you skip draining the tanks?

Yes, the alcohol takes the place of drainingYes, but only in warm weatherNo, though once a month is enoughNo, daily draining is still needed to clear out water and oil

3.In an s-cam brake, what does the s-cam do when the brakes are applied?

It clamps a rotor between caliper padsIt forces the brake shoes outward against the inside of the drumIt drives a wedge between the shoe endsIt releases air out of the brake chamber

4.Why should you avoid pressing the foot brake while the spring brakes are already applied?

It drains the tanks instantlyIt disables the ABS warning lampThe combined force of the springs and air pressure could damage the brakesIt makes the governor cut in early

5.At 55 mph on dry pavement, about how much distance does air brake lag add?

About 100 feetAbout 12 feetAbout 32 feetAbout 450 feet

6.What is the purpose of an alcohol evaporator in some air brake systems?

It lubricates the s-cam and slack adjustersIt raises tank pressure above the governor settingIt lowers the chance of ice forming in the valves during cold weatherIt filters oil out of the compressed air

7.Why do the brakes still work for several applications after the compressor stops running?

The wheels store energy that runs the brakesEach brake chamber holds its own backup canisterThe governor makes air without the compressorThe storage tanks keep a reserve of compressed air on hand

8.How does ABS relate to your normal braking ability?

It replaces your normal brakes entirelyIt weakens normal braking to prevent skidsIt is an add-on that leaves normal braking unchanged and works only near lockupIt always cuts your stopping distance in half

9.If one part of a dual air system loses most of its pressure, what is the result?

Both systems shut down at onceEither the front or rear brakes will not work fully, so stopping takes longerThe parking brakes release on their ownThe compressor doubles its output

10.The low air pressure warning must come on before tank pressure falls below what level?

20 psi100 psi55 psi85 psi