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Skid control and recovery

General Knowledge3 minManual section 2.19

Any time the tires lose their grip on the road surface, you have a skid. Knowing the four causes helps you avoid skids, and knowing the right response helps you get out of one.

Four causes of skids

  • Over-braking: braking too hard and locking the wheels. Skids can also happen when you use the speed retarder on a slippery road.
  • Over-steering: steering more sharply than the vehicle is able to turn.
  • Over-acceleration: giving too much power to the drive wheels so they spin.
  • Driving too fast: most serious skids come from driving too fast for road conditions. Drivers who match their speed to conditions do not need to over-accelerate, over-brake or over-steer.

Drive-wheel skids

By far the most common skid: the rear wheels lose traction from too much braking or acceleration.

  • Acceleration skids are most common on ice or snow. Simply lifting your foot off the accelerator usually ends them. If it is very slippery, push the clutch in, because otherwise the engine may stop the wheels from turning freely and getting their grip back.
  • Rear-wheel braking skids happen when the rear drive wheels lock. Locked wheels have less traction than rolling wheels, so the rear tends to slide sideways to try to “catch up” with the front.
  • In a bus or straight truck, this is a sideways spin out. In a vehicle towing a trailer, the trailer can push the towing vehicle sideways and cause a sudden jackknife.

Correcting a drive-wheel braking skid

  • Stop braking. This lets the rear wheels roll again and keeps them from sliding.
  • Counter-steer. As the vehicle turns back on course, it tends to keep turning. Unless you turn the wheel quickly the other way, you may skid in the opposite direction.

Staying off the brake, turning the wheel quickly, pushing in the clutch and counter-steering take a lot of practice. The best place to practice is a large driving range or skid pad.

Front-wheel skids

Most front-wheel skids are caused by driving too fast for conditions. Other causes: not enough tread on the front tires, and cargo loaded so there is not enough weight on the front axle.

In a front-wheel skid, the front end tends to go straight ahead no matter how much you turn the wheel. On very slick roads the truck may not follow the curve or turn at all.

The only way to stop a front-wheel skid is to let the vehicle slow down. Ease off the hard steering and/or braking, and lose speed as fast as you can without skidding.

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: 2.19

Official CDL handbook · Utah ↗StatesOur editorial approach

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Review questions with answers

  1. Most serious skids are caused by:
    1. Worn wiper blades
    2. Low engine oil
    3. Using cruise control
    4. Driving too fast for road conditions
    Show answer
    Driving too fast for road conditions

    Most serious skids result from driving too fast for conditions.

  2. "Over-steering" means:
    1. Turning the wheels more sharply than the vehicle can turn
    2. Giving too much power to the drive wheels
    3. Braking too hard
    4. Steering with one hand
    Show answer
    Turning the wheels more sharply than the vehicle can turn

    Over-steering is steering more sharply than the vehicle is able to turn.

  3. Skids can also happen when you use the speed retarder:
    1. On dry pavement
    2. When the truck is empty
    3. When the road is slippery
    4. At low rpm
    Show answer
    When the road is slippery

    Skids can occur from using the speed retarder on a slippery road.

  4. By far the most common type of skid is:
    1. A front-wheel skid
    2. A drive-wheel (rear-wheel) skid
    3. A trailer-only skid
    4. A hydroplaning skid
    Show answer
    A drive-wheel (rear-wheel) skid

    The most common skid is when the rear drive wheels lose traction from too much braking or acceleration.

  5. Your drive wheels start spinning on ice when you accelerate. The easy fix is to:
    1. Brake hard
    2. Turn the wheel sharply
    3. Shift to a higher gear
    4. Take your foot off the accelerator (push in the clutch if very slippery)
    Show answer
    Take your foot off the accelerator (push in the clutch if very slippery)

    Acceleration skids stop when you let off the accelerator. On very slippery roads, push in the clutch so the wheels can roll freely.

  6. In a vehicle towing a trailer, a drive-wheel braking skid can cause:
    1. A jackknife
    2. A front-wheel skid
    3. Hydroplaning
    4. Brake fade
    Show answer
    A jackknife

    The trailer can push the towing vehicle sideways, causing a sudden jackknife.

  7. Why do locked rear wheels tend to slide sideways?
    1. They have more traction than rolling wheels
    2. The trailer pulls them straight
    3. Locked wheels have less traction than rolling wheels
    4. The front wheels lose grip first
    Show answer
    Locked wheels have less traction than rolling wheels

    Locked wheels have less traction than rolling wheels, so the rear tends to slide sideways to catch up with the front.

  8. To correct a drive-wheel braking skid, the first step is to:
    1. Brake harder
    2. Stop braking
    3. Accelerate
    4. Turn off the engine
    Show answer
    Stop braking

    Stop braking so the rear wheels can roll again; then counter-steer.

  9. As a skidding vehicle turns back on course, why must you counter-steer quickly?
    1. To lock the wheels again
    2. To turn on the ABS
    3. To make the trailer brake
    4. The vehicle tends to keep turning and may skid the other way
    Show answer
    The vehicle tends to keep turning and may skid the other way

    Unless you quickly turn the wheel the other way, the vehicle may skid in the opposite direction.

  10. The best place to practice skid recovery is:
    1. A large driving range or skid pad
    2. An icy highway at night
    3. A busy parking lot
    4. A mountain downgrade
    Show answer
    A large driving range or skid pad

    Skid recovery takes a lot of practice, best done on a large driving range or skid pad.

  11. Which is a cause of front-wheel skids?
    1. Too much weight on the front axle
    2. New front tires
    3. Not enough weight on the front axle
    4. Driving too slowly
    Show answer
    Not enough weight on the front axle

    Front-wheel skids are mostly from driving too fast, but also from worn front tread and too little weight on the front axle.

  12. In a front-wheel skid, the only way to stop the skid is to:
    1. Turn the wheel harder
    2. Let the vehicle slow down, easing off turning and hard braking
    3. Accelerate
    4. Pull the parking brake
    Show answer
    Let the vehicle slow down, easing off turning and hard braking

    The front end keeps going straight. Stop turning and/or braking so hard and slow down without skidding.

  13. In a front-wheel skid, the front of the vehicle tends to:
    1. Swing toward the trailer
    2. Spin in a circle
    3. Lift off the ground
    4. Go straight ahead no matter how much you turn the wheel
    Show answer
    Go straight ahead no matter how much you turn the wheel

    In a front-wheel skid the front end tends to keep going straight regardless of steering.