SGI Air Brake Practice Test

All 50 questions in this test

Every question and its answer choices. The correct answers and explanations appear when you take the test above.

1. One wheel's brake is poorly adjusted. What happens to the other brakes?

   1. They lock up at the first application
   2. They release slightly to balance the load
   3. They do more than their share and may overheat
   4. They keep working exactly as before

2. How should you connect gladhands?

   1. Clean them, put the seals together at 90° and snap down
   2. Line them up straight and twist clockwise
   3. Connect them with the engine stopped and tanks empty
   4. Grease the rubber seals heavily first

3. After adjusting a manual slack adjuster, how much push rod travel should there be when pulled by hand?

   1. Less than 1/8 inch
   2. 1 to 1 1/2 inches
   3. 1/2 to 3/4 inch
   4. About 2 inches

4. Why are the front brake chamber and slack adjuster mounted on the backing plate?

   1. Because it keeps them away from road heat
   2. Because the front axle has no S-cam
   3. Because the front brakes need more air
   4. Because the axle's steering action would interfere

5. Why should you never take a spring-brake chamber apart?

   1. It lets moisture into the air system
   2. The compressed spring can cause serious injury
   3. It voids the vehicle's inspection decal
   4. It changes the slack adjuster angle

6. What determines how much heat a brake drum can absorb?

   1. The width of the tire tread
   2. The colour of the drum paint
   3. The thickness of the metal
   4. The length of the slack adjuster

7. What does a bobtail proportioning relay valve do when no trailer is attached?

   1. Raises service pressure to the drive axle for shorter stops
   2. Lowers service pressure, so you press the pedal farther
   3. Shuts off the front brakes completely
   4. Applies the spring brakes automatically

8. After adjusting, you tap the brake drum with a hammer and hear a dull sound. What does it mean?

   1. The brake is perfectly adjusted
   2. The lining is new and still bedding in
   3. The brake is dragging and needs readjusting
   4. The drum is cracked and must be replaced

9. What is the minimum pressure at which the governor should cut the compressor back in?

   1. 80 psi (552 kPa)
   2. 120 psi (828 kPa)
   3. 60 psi (414 kPa)
   4. 100 psi (690 kPa)

10. In a dual-circuit system, the secondary circuit develops a major leak. What happens?

    1. All service brakes fail at once
    2. The primary circuit keeps working on its own
    3. The compressor shuts down to save air
    4. The spring brakes apply immediately

11. About how long is brake lag in a properly maintained air brake system?

    1. About 4/10 of a second
    2. About 1 1/2 seconds
    3. About 2 seconds
    4. About 1/100 of a second

12. The service line to the trailer ruptures. When will you notice an effect?

    1. Immediately, as the trailer brakes apply
    2. Only when the trailer-supply valve is closed
    3. Never, the tractor protection valve seals it
    4. Only when you make a brake application

13. Single unit, engine off, full foot brake held: how much air loss is allowed after the initial drop?

    1. No more than 3 psi in two minutes
    2. No more than 4 psi in one minute
    3. No more than 10 psi in one minute
    4. No more than 1 psi in one minute

14. At what pressure must the governor cut out the compressor?

    1. Between 80 and 100 psi
    2. Between 60 and 70 psi
    3. Exactly 150 psi
    4. Between 120 and 145 psi

15. Why are spring brakes a reliable parking brake?

    1. They use the highest air pressure in the system
    2. They can only be released with a wind-off bolt
    3. They lock the transmission as well as the wheels
    4. They are held on by spring pressure and need no air

16. At about what temperature do most brake linings work best?

    1. Around 250 °C
    2. Around 30 °C
    3. Around 120 °C
    4. Around 300 °C

17. Which two valves make up the tractor protection system?

    1. The relay valve and the quick-release valve on the axle
    2. The foot valve and the trailer hand control valve
    3. Trailer-supply valve and tractor protection valve
    4. The safety valve and the governor

18. Why might badly adjusted brakes go unnoticed?

    1. They only fail in warm weather
    2. The low air warning hides them
    3. They make the pedal feel harder
    4. They seem fine under light braking

19. What is the purpose of the one-way check valve between the supply and service reservoirs?

    1. It warns the driver of low pressure
    2. It stops air flowing back if the supply side fails
    3. It lets air flow both ways to balance tanks
    4. It releases excess pressure into the air

20. How are spring brakes applied and released?

    1. Applied by hydraulic fluid, released by air
    2. Applied and released by air pressure
    3. Applied by spring force, released by air pressure
    4. Applied by air pressure, released by spring force

21. A truck has hydraulic brakes with an air-powered assist. Do you need an A endorsement?

    1. Only if the truck has three axles
    2. Only for trips outside Saskatchewan
    3. No, air-over-hydraulic brakes are exempt
    4. Yes, any air component at all requires it

22. The supply line to the trailer ruptures. What happens to the trailer brakes?

    1. They go into an emergency application at once
    2. They release completely
    3. They wait until the next foot application
    4. They work only with the hand valve

23. How often must automatic slack adjusters be checked?

    1. Weekly
    2. Only at the PMVI inspection
    3. Daily
    4. Monthly

24. Why is the first reservoir also called the wet tank?

    1. It sits closest to the fuel tank
    2. It is the only tank fitted with a draincock
    3. It is filled with antifreeze in the winter
    4. Most water and oil from the compressor collect there

25. Why should you release the parking brakes before a full foot-brake application test?

    1. To avoid compounding the forces on the brake parts
    2. To keep the low air warning from sounding
    3. To stop the trailer from rolling forward
    4. To let the compressor cut in sooner

26. Which driver does not need an air brake A endorsement?

    1. A city transit bus driver
    2. A school bus driver with an S endorsement
    3. A tractor-trailer driver on a highway
    4. A farm-licensed Class 3 truck driver

27. What colour and shape is the trailer-supply valve control usually?

    1. A red octagonal button
    2. A blue round knob
    3. A green square switch
    4. A yellow diamond-shaped button

28. During a combination pre-trip test you break the supply line. What should happen?

    1. Nothing happens until the foot valve is pressed
    2. Trailer brakes release and the tractor loses all air
    3. The low air warning sounds at 100 psi
    4. Trailer brakes apply and tractor air shuts off at 20 psi or more

29. How often must air reservoirs be completely drained when the vehicle is in use?

    1. Only when the air dryer fails
    2. Once a week
    3. Once a day
    4. Once a month

30. All air has been lost and the spring brakes have applied. How can the vehicle be moved?

    1. Pump the foot valve several times until the brakes release
    2. Repair and recharge, or cage the springs
    3. Pull the park brake valve out and then push it back in
    4. Use the trailer hand valve to release them

31. Air at 120 psi acts on a 30 square inch diaphragm. How much force does it produce?

    1. 3,600 lb.
    2. 36,000 lb.
    3. 360 lb.
    4. 150 lb.

32. At what supply-line pressure does the tractor protection valve open its service-line port?

    1. 60 psi
    2. 20 psi
    3. 45 psi
    4. 100 psi

33. How long should it take the compressor to raise pressure from 85 to 100 psi at 600–800 rpm?

    1. Less than ten seconds
    2. Less than two minutes
    3. Less than five minutes
    4. Exactly three minutes

34. The safety valve on the supply reservoir blows off air. What does this indicate?

    1. A problem with the governor
    2. A worn brake lining
    3. Normal operation in cold weather
    4. A leak in the service line

35. With a push-to-release park valve, at about what pressure do spring brakes begin to drag?

    1. About 10 psi
    2. About 70 psi
    3. About 45 psi
    4. About 100 psi

36. If both the weight and the speed of a truck are doubled, how much more stopping power is needed?

    1. Eight times as much
    2. Sixteen times as much
    3. Four times as much
    4. Twice as much

37. Your tractor-trailer starts to skid. When might gentle use of the hand valve help?

    1. Whenever the road is icy
    2. When the tractor skids, to help straighten the unit
    3. Only to hold the unit still when parked on a grade
    4. When the trailer is skidding sideways behind you

38. Pulling on the slack adjuster, you measure 1 1/8 in. of push rod travel. What should you do?

    1. Drain the reservoirs and recheck
    2. Have the brake adjusted before driving
    3. Nothing; up to 2 in. is acceptable
    4. Add air pressure and recheck

39. Why is a relay valve installed near the rear brake chambers of a long vehicle?

    1. To reduce brake lag at the rear wheels
    2. To lower air pressure to the front brakes
    3. To hold the brakes on when parked
    4. To dry the air before it reaches the brakes

40. What is blended air?

    1. Air taken from both the primary and secondary circuits
    2. Air that has passed through the air dryer
    3. Air mixed with oil to lubricate valves
    4. Air from the trailer and tractor tanks together

41. Stopping distance is made up of which three parts?

    1. Reaction time, brake lag and braking distance
    2. Speed, weight and tire pressure
    3. Brake fade, brake lag and road surface
    4. Following distance, reaction time and gear

42. When does the service line contain air?

    1. Whenever the trailer-supply valve is open
    2. Only when a brake application is made
    3. Whenever the engine is running
    4. Only when the parking brakes are applied

43. An automatic slack adjuster is badly out of adjustment. What may bring it back into adjustment?

    1. Up to 12 applications of about 100 psi
    2. One brake application at about 20 psi
    3. Turning the adjusting nut by hand each morning
    4. Driving with the park brake on

44. What does a front axle ratio valve do during light brake applications?

    1. Reduces pressure to the front brakes
    2. Doubles the application pressure to the front brakes
    3. Shuts off the rear brakes
    4. Applies only the trailer brakes

45. What does 'compounding' the brakes mean?

    1. Draining both reservoirs at the same time
    2. Applying the service brakes while the park brake is on
    3. Using the hand valve and foot valve together
    4. Pumping the brakes on a downgrade

46. What is the final factor that determines whether a vehicle stops?

    1. The thickness of the brake linings
    2. Traction between the tires and the road
    3. The size of the brake chambers
    4. The air pressure in the reservoirs

47. Which function belongs to the relay emergency valve on a trailer?

    1. It dries the air before it reaches the trailer tank
    2. It controls the tractor's spring parking brakes
    3. Applies the trailer brakes if the supply line parts
    4. It lowers pressure to the trailer's front axle

48. On a type 30 chamber, at how much slack must a brake be adjusted?

    1. 1/4 inch (6.4 mm)
    2. 2 1/2 inches (63.5 mm)
    3. 2 inches (50.8 mm)
    4. 1 inch (25.4 mm)

49. What limits the maximum pressure you can apply to the brakes?

    1. The strength of your leg
    2. The air pressure in the reservoir
    3. The size of the foot valve
    4. The governor cut-in setting

50. In a dual-circuit system on a two-axle truck, which brakes does the primary reservoir normally operate?

    1. The spring parking brakes
    2. The trailer brakes only
    3. The front service brakes
    4. The rear service brakes