California CDL — Air Brakes Practice Test 7

1.How do you test the service brakes during the final air brake check?

Set the parking brake and pull gently against it in a low gearRoll forward slowly at about 5 mph and press the brake pedal firmly, watching for pulling or a delayed stopPump the pedal with the engine off until the warning buzzer soundsHold the pedal down for one minute and watch the air gauge

2.Your vehicle has automatic slack adjusters, and you find a brake that is out of adjustment. What does the handbook recommend?

Get it to a repair shop promptly, because a mechanical problem is likelyAdjust it by hand at every pre-trip inspection as routine practiceIgnore it, since automatic adjusters correct themselves within a few milesDisconnect that brake chamber and keep driving on the remaining brakes

3.Your service brakes stop working on a mountain downgrade because they have overheated and faded. What is your best option?

Swerve from side to side to scrub off speedShift into neutral so the drivetrain cannot push the vehicleSteer onto the shoulder and hold the horn downUse an escape ramp if one is available

4.Dual air brake systems are used on most heavy-duty vehicles. What safety advantage does a dual system give you?

It doubles the vehicle's braking power on steep downgradesIt lets the compressor rest while one system is in useIt allows the trailer and tractor to brake at different ratesBecause the two systems are separate, losing air in one still leaves the brakes on the other system working

5.You test air leakage on a single vehicle by turning off the engine, releasing the service brake, and timing the pressure drop. What is the maximum acceptable leakage rate with the brakes released?

Less than 4 psi in one minuteLess than 6 psi in one minuteLess than 2 psi in one minuteLess than 10 psi in one minute

6.Your straight truck has working anti-lock brakes on every axle, and it is the only kind of vehicle you drive. How may you brake in an emergency stop?

You must use stab braking, releasing each time the wheels lockYou should brake lightly and steer onto the shoulder insteadYou should pull the parking brake knob to add the spring brakesYou can apply the brakes fully

7.With air brakes, how long does it take after you push the brake pedal for air to reach the brakes through the lines?

No time at all; they apply the instant you push the pedal1/2 second or moreAbout one-tenth of a secondAbout one-quarter of a second

8.If you double your speed from 25 mph to 50 mph, what happens to the distance your vehicle needs to brake to a stop?

It roughly doublesIt roughly quadruplesIt stays about the same if the brakes are well adjustedIt increases by about 10 percent

9.Does an anti-lock braking system (ABS) shorten the distance you need to stop?

Yes — it always cuts stopping distance roughly in halfNot necessarily — its benefit is helping you keep control during hard brakingYes — but only on dry pavementNo — it always lengthens stopping distance because it releases the brakes

10.Air brakes are really three braking systems in one. Which of them stops the vehicle if the brake system fails, using parts of the other two?

The service brake systemThe emergency brake systemThe parking brake systemThe anti-lock braking system