Nebraska CDL — Air Brakes Practice Test 9

11.What does the manual mean by 'brake lag' on a vehicle with air brakes?

The time a driver takes to notice a hazardThe distance covered while the driver's foot moves to the pedalThe time the compressor needs to refill the tanksThe time the brakes take to work once the pedal has been pushed

12.Which of these is NOT one of the brake lining defects the walk-around check tells you to look for?

Linings that are looseLinings soaked with oil or greaseLinings that are a lighter shade than the drumLinings worn dangerously thin

13.During the in-vehicle part of Nebraska's vehicle inspection test, you check the ABS indicator on the dashboard of a combination vehicle. What should the trailer's ABS light do?

The ABS light at the rear of the trailer on the driver's side should come on and then go offThe light on the passenger side should stay lit the whole timeIt should flash until the vehicle is moving faster than five mphNothing; the trailer's ABS light is checked only on the road test

14.Which order matches how an s-cam brake applies after you press the pedal?

Air enters the slack adjuster, the s-cam moves out, the push rod twists, and the camshaft spreads the shoes against the drumThe camshaft twists, air enters the brake chamber, the shoes spread, and then the push rod moves outAir enters the brake chamber, the push rod moves out, the slack adjuster moves, the camshaft twists, and the s-cam spreads the shoes against the drumThe push rod moves out, air leaves the brake chamber, the s-cam pulls the shoes together, and the drum turns the camshaft

15.Where does the manual say a trailer's yellow ABS malfunction lamp is mounted?

On the right side, at the rear corner onlyIn the center of the rear doorsUnderneath, next to the electronic control unitOn the left side, at either the front or the rear corner

16.A truck tractor with air brakes was built in 1995, before ABS was required on tractors. What does the manual say about whether it might have ABS?

It cannot; ABS did not exist for air brakes before 1997It must; ABS has been required on every tractor since 1975It might; many commercial vehicles made before the required dates were given ABS voluntarilyIt might, but only if it pulls a trailer built after 1998

17.The manual says you may or may not stop faster with ABS. What does it say ABS should still let you do during a hard stop?

Lock the wheels on purpose to shorten the stopKeep steering, so you can go around an obstacle, and avoid a skid from braking too hardFollow the vehicle ahead more closelyUse the parking brake to help slow the vehicle

18.The Step 7 check ends with a low-speed test of the service brakes. Why does the manual say this test is worth doing?

It warms the drums so the linings grip betterIt can reveal brake problems that would otherwise stay hidden until a real stop in trafficIt resets the automatic slack adjustersIt bleeds water out of the air tanks

19.What happens at the brakes when you push the brake pedal of an air-braked vehicle down harder?

More air pressure is applied to the brakesThe compressor cuts outThe spring brakes take over from the service brakesPressure at the brakes stays the same while the tanks refill faster

20.Your low air pressure warning comes on while you are driving. The manual tells you to stop and park safely as soon as possible. What does it suggest might be wrong?

The brakes are probably too coldThe alcohol evaporator is likely emptyThe system may have an air leakThe governor has probably cut out early