Rhode Island CDL — Air Brakes: Safe Driving Practices Practice Test

Question 1

You are about to tow an older trailer, built before antilock brakes were required on towed units, and you cannot tell whether it has ABS. What does the manual suggest you check?

Accepted Answer

Underneath the trailer, for an ECU and for wheel speed sensor wiring running out from behind the brakes — For towed units made before ABS became mandatory, it can be hard to know whether it was fitted. The manual's tip is to look beneath the unit for the ABS electronic control unit and for wheel speed sensor wiring coming out of the brakes.

Answer

The gladhands, since trailers with ABS use a different coupler color

Answer

The air tank drains, since trailers with ABS have a second drain valve on each tank

Answer

The trailer tires, since tires on ABS trailers carry a special sidewall marking

Question 2

Which of these air-braked vehicles was NOT required to come equipped with antilock brakes?

Accepted Answer

A bus built in January 1998 — Air-braked truck tractors needed ABS if they were built March 1, 1997 or later. Other air-braked vehicles, including trucks, buses, trailers and converter dollies, needed it from March 1, 1998 onward, so a bus from January 1998 came before its cutoff.

Answer

A truck tractor built in June 1997

Answer

A trailer built in May 1998

Answer

A converter dolly built in 1999

Question 3

Checking an s-cam brake, you find a slack adjuster that moves about an inch and a half at the point where the pushrod attaches. What does the manual say?

Accepted Answer

It probably needs adjustment, so adjust it or have it adjusted — Movement of more than about one inch where the pushrod meets the slack adjuster usually means the brake needs adjusting. Too much brake slack can make a vehicle very hard to stop.

Answer

That is normal free play for an s-cam brake

Answer

It needs adjustment only if the truck is loaded

Answer

The movement shows that the spring brakes are applied

Question 4

The manual says brakes can drift out of adjustment quickly. Under what condition does it say this is especially likely?

Accepted Answer

When the brakes are hot — Brakes can lose adjustment fast, especially when they are hot, which is why the manual tells you to check brake adjustment often.

Answer

When the truck sits parked overnight

Answer

When the air tanks are full

Answer

When the ABS lamp is lit

Question 5

A straight truck's air system is fully charged. You shut off the engine, push in the parking brake knob and time the gauge. Pressure drops 2.5 psi in one minute. How does that compare with the manual's limit?

Accepted Answer

It is too much; a single vehicle should lose less than 2 psi in a minute with the brakes released — With the system fully charged, the engine off and the parking brake released, a single vehicle should lose less than 2 psi per minute (combination vehicles, less than 3). Find and fix leaks before driving, or you could lose your brakes on the road.

Answer

It is fine, since a single vehicle may lose up to 3 psi a minute this way

Answer

It is fine, since only combination vehicles are timed

Answer

It is too much only if the truck has ABS

Question 6

Which pairing of warning device and its usual color matches the manual?

Accepted Answer

Low air pressure warning: usually a red light; ABS malfunction lamp: yellow — The low air pressure warning is usually a red light, sometimes with a buzzer. Vehicles with ABS have yellow malfunction lamps that tell you when something is not working.

Answer

Low air pressure warning: usually a yellow light; ABS malfunction lamp: red

Answer

Low air pressure warning: usually a green light; ABS malfunction lamp: blue

Answer

Low air pressure warning and ABS malfunction lamp: both red

Question 7

In the leakage test done with the foot brake fully applied, how long do you hold the pedal down while watching the gauge?

Accepted Answer

One minute — With pressure at governor cutoff, the engine off and the parking brake (plus the tractor protection valve on a combination) released, you hold the foot brake down for one minute and see how far the gauge falls.

Answer

Ten seconds

Answer

Five minutes

Answer

Until the low air warning comes on

Question 8

Before the applied-brake leakage test, you build air up to governor cutoff. What range does the manual give for that cutoff pressure?

Accepted Answer

120 to 140 psi — For the leakage check with the foot brake held down, you first build pressure to governor cutoff, which the manual puts at 120 to 140 psi, and then shut off the engine.

Answer

60 to 85 psi

Answer

85 to 100 psi

Answer

150 to 175 psi

Question 9

Your truck's air tanks have manually operated drain valves. How is this type of drain opened?

Accepted Answer

By turning the valve a quarter of a turn, or by pulling on a cable — Each tank has a drain valve at its bottom. The manual type opens with a quarter of a turn or a pull on a cable, and you do the draining yourself.

Answer

By pressing the brake pedal five times with the engine off

Answer

By pushing in the yellow parking brake knob

Answer

It opens by itself whenever the governor cuts out

Question 10

During the governor check, the compressor does not cut in and out at about the pressures the manufacturer specifies. Why does the manual treat this as something to fix?

Accepted Answer

A faulty governor might not hold enough air in the system to drive safely — The governor decides when the compressor pumps air into the tanks. If it does not cut in and cut out as it should, the system may not keep the air pressure you need to drive safely, so it may need repair.

Answer

The governor sets how hard the brakes apply, so braking would be uneven

Answer

A faulty governor makes the ABS malfunction lamp stay on

Answer

It matters only on vehicles built before 1975

Question 11

How does a drum brake actually slow the vehicle?

Accepted Answer

The shoes and linings press on the inside of the drum, and the friction slows the wheel while making heat — When you brake, the shoes and their linings are forced against the inside of the drum. The friction slows the vehicle and also creates heat, and too much heat can make the brakes quit.

Answer

Air pressure pushes directly against the tire

Answer

A caliper squeezes the outside of the drum

Answer

A pin locks the axle in place

Question 12

You need to troubleshoot a brake adjustment problem on automatic slack adjusters. What should you consult first, and why?

Accepted Answer

The maker's own service manual, because adjusters from different manufacturers do not all work alike — Automatic slack adjusters are built by several manufacturers and do not all work the same way, so the specific maker's service manual should be checked before you troubleshoot an adjustment problem.

Answer

The ABS certification label, because it lists adjustment limits

Answer

The application pressure gauge, because it shows adjuster wear

Answer

Nothing, because all automatic adjusters operate the same way

Rhode Island CDL — Air Brakes: Safe Driving Practices practice test

Study questions with answers

1. You are about to tow an older trailer, built before antilock brakes were required on towed units, and you cannot tell whether it has ABS. What does the manual suggest you check?

2. Which of these air-braked vehicles was NOT required to come equipped with antilock brakes?

3. Checking an s-cam brake, you find a slack adjuster that moves about an inch and a half at the point where the pushrod attaches. What does the manual say?

4. The manual says brakes can drift out of adjustment quickly. Under what condition does it say this is especially likely?

5. A straight truck's air system is fully charged. You shut off the engine, push in the parking brake knob and time the gauge. Pressure drops 2.5 psi in one minute. How does that compare with the manual's limit?

6. Which pairing of warning device and its usual color matches the manual?

7. In the leakage test done with the foot brake fully applied, how long do you hold the pedal down while watching the gauge?

8. Before the applied-brake leakage test, you build air up to governor cutoff. What range does the manual give for that cutoff pressure?

9. Your truck's air tanks have manually operated drain valves. How is this type of drain opened?

10. During the governor check, the compressor does not cut in and out at about the pressures the manufacturer specifies. Why does the manual treat this as something to fix?

11. How does a drum brake actually slow the vehicle?

12. You need to troubleshoot a brake adjustment problem on automatic slack adjusters. What should you consult first, and why?

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