New Mexico CDL — Air Brakes Practice Test 5

1.Which order matches the way the manual says an air-operated disc brake applies?

Air pressure reaches the brake chamber, the push rod drives a wedge, and the shoes spread against the discAir pressure turns the power screw, the screw moves the slack adjuster, and the s-cam clamps the discAir pressure reaches the brake chamber, the slack adjuster turns the power screw, and the caliper's pads clamp the discThe caliper's pads clamp the disc, the power screw turns, and air pressure is then let into the brake chamber

2.You are building pressure in a New Mexico truck with a dual air system. The low air warning light and buzzer shut off when both gauges reach 58 psi. How does that compare with Section 5 of New Mexico's manual?

It is too low; the manufacturer's shut-off value has to be greater than 60 psiIt is fine; the warning may shut off anywhere above 45 psiIt is fine; the warning should shut off once either system passes 55 psiIt is too low; the warning has to stay on until both systems reach governor cut-out

3.The manual describes three kinds of foundation brake. In which one does the brake chamber push rod act on the shoes' mechanism directly, with no slack adjuster named in between?

S-cam brakesAir disc brakesNone; all three are described with a slack adjusterWedge brakes

4.During the Step 7 leakage test the pressure drop is more than the manual allows, and the driver decides to deal with it after the day's run. What does the manual warn could happen?

The governor could cut in more often and wear out the beltThe ABS lamp could stay lit until the next bulb checkThe alcohol evaporator could run dryThe brakes could be lost while driving

5.Four drivers run the Step 7 air leakage tests with the engine off. Whose result is more than the manual allows?

A straight truck, brakes released: 1.5 psi lost in one minuteA tractor-trailer, brakes released: 2.5 psi lost in one minuteA tractor-trailer, foot brake held down: 4.5 psi lost in one minuteA straight truck, foot brake held down: 2.5 psi lost in one minute

6.A trainee makes four statements about drum brakes. Which one does NOT match the manual?

The shoes and linings press against the outside of the drumThe drums are found at each end of the axlesThe wheels bolt onto the drumsThe friction that slows the vehicle at the drum also produces heat

7.The Step 7 check times air leakage twice, once with the brakes released and once with the foot brake held down. What do the two tests have in common?

The engine runs at a fast idle and the parking brake is setThe electrical power is off and the air tanks have been drainedThe vehicle is rolling forward at about five mphThe engine is off and the parking brake is released

8.Section 11 has you check a drum brake for cracks, dents or holes. Which fastener problem does it also tell you to look for?

Bolts that are loose or missingLug nuts with rust trails around themCotter pins missing from the slack adjustersClamps that have been welded in place

9.You are assigned a truck built in 1990. Based on the manual's statement about automatic slack adjusters, what can you assume about this truck?

Nothing for certain; the manual's statement covers vehicles built since 1994It must have automatic slack adjusters, as every air-braked vehicle on the road doesIt cannot have slack adjusters of any kindIt has automatic slack adjusters that never need to be checked

10.An applicant passes the air brakes knowledge test, then takes the CDL skills test in a truck that has hydraulic brakes. What does Section 1 say about the L restriction?

It goes on the license, because the skills test was not taken in an air-braked vehicleIt does not apply, because passing the knowledge test is what keeps it off the licenseIt is swapped for the Z restriction on full air brakesIt applies only until the license is first renewed