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Quick stops, brake failure and tire failure

General Knowledge5 minManual section 2.17.2–2.17.4

If someone pulls out in front of you, your first reaction is to hit the brakes. That is fine if you have room and you brake the right way. This lesson covers the two safe emergency braking methods, what to do when brakes fail, and how to handle a tire failure.

How to stop quickly and safely

Brake so the vehicle stays in a straight line and you can still turn if needed. Use controlled braking or stab braking.

  • Controlled braking: brake as firmly as possible while keeping the wheels from locking. Keep steering movements very small. If you need a bigger steering change, or if the wheels lock, release the brakes, then re-apply as soon as you can.
  • Stab braking: press the brakes all the way. Release when the wheels lock. As soon as the wheels start rolling, brake fully again. It can take up to 1 second for wheels to start rolling after you release. If you brake again before they roll, the vehicle will not straighten out.
  • Do not jam on the brakes. Pushing the pedal as hard as you can and holding it keeps the wheels locked and causes a skid. With skidding wheels you cannot control the vehicle.

Note: stab braking is for vehicles without working ABS. With ABS on all wheels, see the ABS lesson.

Hydraulic brake failure

Brakes kept in good condition rarely fail. Most hydraulic brake failures have one of two causes: loss of hydraulic pressure, or brake fade on long hills. (Air brakes are covered in Section 5.)

Loss of hydraulic pressure: the system will not build pressure, and the pedal feels spongy or goes to the floor. What to do:

  • Downshift. A lower gear helps slow the vehicle.
  • Pump the brakes. Pumping sometimes builds enough pressure to stop.
  • Use the parking brake. The parking (emergency) brake is separate from the hydraulic system, so it can slow you. But keep the release button pressed or the release lever pulled while you apply it, so you can control the pressure and keep the wheels from locking.
  • Look for a way out as you slow: a side street, an open field or an escape ramp. Heading uphill helps slow and stop the vehicle. After you stop, make sure the vehicle does not roll backward: put it in low gear, set the parking brake, and if needed roll back into something that will stop it.

Brake failure on downgrades

If you keep your speed down and brake the right way, brakes will almost never fail on a long downgrade. After they fail, you must look outside your vehicle for something to stop it.

  • Your best hope is an escape ramp. Signs will tell you about it. Use it. You will usually find them a few miles down from the top of the grade. They prevent injury or damage for hundreds of drivers every year.
  • Some ramps use soft gravel that resists the vehicle and stops it. Others slope uphill: the climb stops the vehicle and the soft gravel keeps it from rolling.
  • If your brakes give out on a downgrade and a ramp is available, take it. If you do not, your chance of a serious crash may be much greater.
  • If there is no ramp, take the least hazardous escape route — an open field or a side road that levels off or climbs. Move as soon as you know the brakes do not work. The longer you wait, the faster you go and the harder it is to stop.

Recognize tire failure

Knowing quickly that a tire failed gives you more time to react. The main signs:

  • Sound: the loud bang of a blowout. It can take a few seconds for the vehicle to react, so you may think it was another vehicle. Any time you hear a tire blow, assume it is yours.
  • Vibration: heavy thumping or vibration may mean a tire has gone flat. With a rear tire, this may be the only sign you get.
  • Feel: heavy steering usually means a front tire failed. A failed rear tire may make the vehicle slide back and forth (fishtail), but dual rear tires usually prevent this.

Respond to tire failure

  • Hold the steering wheel firmly. A failed front tire can twist the wheel out of your hands. The only protection is a firm two-hand grip at all times.
  • Stay off the brake. Braking when a tire has failed can cause loss of control. Unless you are about to hit something, wait until the vehicle slows down. Then brake very gently, pull off the road, and stop.
  • Check the tires. After stopping, get out and check all tires, even if the vehicle seems to handle fine. If one of your dual tires fails, looking may be the only way you find out.

References and scope

The topic reference is listed below. Sources support verification; the lesson itself is here. The current content needs technical and language review before public launch.

Manual reference: 2.17.2–2.17.4

Official CDL handbook · Utah ↗StatesOur editorial approach

Put it into practice

Educational questions with explanations. The answer review also works without the interactive quiz.

Preparing your questions…

Review questions with answers

  1. With the controlled braking method, you:
    1. Push the pedal all the way and hold it
    2. Brake as hard as you can without locking the wheels, keeping steering movements very small
    3. Release and re-apply every 5 seconds
    4. Use only the parking brake
    Show answer
    Brake as hard as you can without locking the wheels, keeping steering movements very small

    Controlled braking: brake as hard as possible without lockup, with only small steering movements. If wheels lock or you need to steer more, release, then re-apply.

  2. During controlled braking, the wheels lock up. You should:
    1. Hold the brakes down harder
    2. Pull the parking brake
    3. Turn the wheel sharply
    4. Release the brakes, then re-apply as soon as you can
    Show answer
    Release the brakes, then re-apply as soon as you can

    If the wheels lock, or you need a larger steering change, release the brakes and re-apply them as soon as possible.

  3. In stab braking, after you release the brakes it can take up to ______ for the wheels to start rolling again.
    1. 1 second
    2. 5 seconds
    3. 1/10 second
    4. 3 seconds
    Show answer
    1 second

    It can take up to one second. If you re-apply before the wheels roll, the vehicle will not straighten out.

  4. In stab braking, you re-apply the brakes fully:
    1. Before the wheels stop
    2. Only after the vehicle stops
    3. As soon as the wheels start rolling again
    4. Every 3 seconds no matter what
    Show answer
    As soon as the wheels start rolling again

    Brake all the way, release when wheels lock, and brake fully again once the wheels start rolling.

  5. Emergency braking means pushing the brake pedal as hard as you can and holding it.
    1. True
    2. False
    Show answer
    False

    False. Jamming on the brakes keeps the wheels locked and causes a skid, and you cannot control a skidding vehicle.

  6. Most hydraulic brake failures happen because of:
    1. Worn wiper blades and low oil
    2. A bad battery or alternator
    3. Loss of hydraulic pressure or brake fade on long hills
    4. Cold weather and snow
    Show answer
    Loss of hydraulic pressure or brake fade on long hills

    The two main reasons are loss of hydraulic pressure and brake fade on long hills.

  7. Your hydraulic brake pedal suddenly goes to the floor. Which action is correct?
    1. Downshift, pump the brakes, and use the parking brake while holding its release
    2. Turn off the engine
    3. Shift to neutral
    4. Stand on the pedal harder
    Show answer
    Downshift, pump the brakes, and use the parking brake while holding its release

    Downshift, pump the brakes to try to build pressure, and use the separate parking brake while holding the release to avoid lockup.

  8. Why can the parking brake help when hydraulic pressure is lost?
    1. It doubles the hydraulic pressure
    2. It locks all wheels instantly
    3. It turns on the ABS
    4. It is separate from the hydraulic brake system
    Show answer
    It is separate from the hydraulic brake system

    The parking (emergency) brake works apart from the hydraulic system, so it can still slow the vehicle.

  9. A runaway truck with no brakes finally stops while going uphill. What should the driver do next?
    1. Shift to neutral and get out
    2. Put it in low gear, set the parking brake, and if needed roll back into something that will stop it
    3. Let it roll back to flat ground
    4. Restart the engine and keep driving
    Show answer
    Put it in low gear, set the parking brake, and if needed roll back into something that will stop it

    Make sure the vehicle does not roll backward: low gear, parking brake, and if necessary back into an obstacle.

  10. Your brakes fail on a downgrade and there is an escape ramp ahead. You should:
    1. Skip it unless the truck is empty
    2. Try to downshift to neutral first
    3. Use the escape ramp
    4. Wait to see if the brakes cool down
    Show answer
    Use the escape ramp

    If your brakes give out on a downgrade and an escape ramp is available, use it.

  11. Escape ramps are usually located:
    1. A few miles from the top of the downgrade
    2. Only at the very bottom of the hill
    3. Every half mile
    4. Only on the uphill side
    Show answer
    A few miles from the top of the downgrade

    Ramps are usually a few miles from the top of the downgrade, and signs tell you about them.

  12. Your brakes fail and there is no escape ramp. Which is the best choice?
    1. Wait until the bottom of the hill
    2. Steer into oncoming traffic lanes
    3. Shift to neutral
    4. Take an open field or side road that flattens out or turns uphill, as soon as possible
    Show answer
    Take an open field or side road that flattens out or turns uphill, as soon as possible

    Take the least hazardous escape route right away; waiting only makes the vehicle faster and harder to stop.

  13. Heavy steering is most likely a sign that:
    1. A rear tire has failed
    2. A front tire has failed
    3. The trailer brakes are dragging
    4. The fifth wheel is unlocked
    Show answer
    A front tire has failed

    If steering feels heavy, one of the front tires has probably failed.

  14. You hear a loud bang like a tire blowing out. You should:
    1. Assume it was another vehicle
    2. Brake hard immediately
    3. Assume it is your tire
    4. Speed up to get past it
    Show answer
    Assume it is your tire

    It can take a few seconds for your vehicle to react, so any time you hear a tire blow, assume it is yours.

  15. After a tire fails, the correct first actions are:
    1. Hold the wheel firmly and stay off the brake until the vehicle slows
    2. Brake hard and steer to the shoulder
    3. Shift to neutral and coast
    4. Turn the wheel sharply toward the failed tire
    Show answer
    Hold the wheel firmly and stay off the brake until the vehicle slows

    Grip the wheel firmly and stay off the brake unless you are about to hit something. When slower, brake gently, pull off and stop.

  16. Why should you check all tires after a tire failure even if the vehicle handles fine?
    1. Inspectors require a photo
    2. To cool the brakes
    3. To reset the ABS
    4. A failed dual tire may only be found by looking at it
    Show answer
    A failed dual tire may only be found by looking at it

    If one of your duals goes, getting out and looking may be the only way you know.

  17. With a rear tire failure, the only sign you may get is:
    1. Heavy steering
    2. Thumping or heavy vibration
    3. A warning light
    4. Smoke from the exhaust
    Show answer
    Thumping or heavy vibration

    Heavy thumping or vibration may mean a tire is flat; with a rear tire, it may be the only sign.