Vermont CDL — Air Brakes Practice Test 10

1.In an s-cam brake, air pressure pushes the rod out of the brake chamber and moves the slack adjuster. What does the slack adjuster's movement twist?

The power screwThe wedgeThe return springThe brake camshaft

2.The manual explains how too much heat produces brake fade. Which of these is NOT part of that explanation?

Chemical changes in the lining cut the frictionThe air tanks lose pressure as the drums heat upThe drums expandShoes and linings must travel farther and press with less force

3.Which pairing of governor setting and approximate tank pressure matches the manual?

Cut-in around 125 psi, cut-out around 150 psiCut-out around 100 psi, cut-in around 125 psiCut-out around 125 psi, cut-in around 100 psiCut-in around 55 psi, cut-out around 100 psi

4.Air tank drain valves come in two types. How does the automatic type differ from the manual type?

It drains only when the engine is switched offIt removes the water but leaves the oil for the driverIt works only on the tank nearest the compressorIt expels the water and oil by itself instead of waiting for the driver to open it

5.Vermont requires the air brake knowledge test, plus a suitably equipped skills-test vehicle, to be licensed for air-braked commercial vehicles. To which other brake system does the manual apply the same two requirements?

Hydraulic brakes with a vacuum boosterAir over hydraulic brakesElectric trailer brakesEngine compression brakes

6.On the vehicle inspection test, your truck's air compressor is driven by gears, so there is no compressor belt to check. What does Section 11 have you do?

Skip the compressor and move on without commentFail the item, since only belt-driven compressors are allowedTell the examiner it is not belt driven and check that it works properly, is undamaged, is not leaking and is securely mountedRemove the compressor cover so the examiner can see the gears

7.How does the manual compare inspecting a vehicle with air brakes to inspecting one without them?

The air-braked vehicle needs an entirely separate inspection methodThe air-braked vehicle needs fewer checks because the system tests itselfThe air-braked vehicle has extra items to check, worked into the same seven-step methodOnly the trailer of an air-braked rig needs inspecting

8.You run the applied-brake leakage test on a tractor-trailer: engine off, parking brake and tractor protection valve released, foot brake held down. In one minute the gauge falls 5 psi. What does the manual say?

The loss is too great; with the foot brake applied, a combination may drop no more than 4 psi in a minuteThe loss is acceptable; a combination may drop up to 6 psi in a minuteThe loss is too great; no vehicle may drop more than 1 psi in a minuteThe loss does not matter, because leakage limits apply only to single vehicles

9.For a vehicle to be controlled safely, each brake has to carry its part of the load. Which brakes does the manual say drop out of that effort first?

The ones that are out of adjustmentThe ones on the steering axleThe ones nearest the compressorThe ones with the newest linings

10.You climb into an older air-braked truck and find a round blue knob on the dash instead of a yellow diamond-shaped one. According to the manual, what might that knob be?

The trailer air supply controlThe front brake limiting controlThe alcohol evaporator switchThe parking brake control