How to Size Wheel Chocks

by John Walker

Wheel chocks are defined as any wedge-shaped object placed in front or behind a tire to prevent the vehicle from rolling. The chocks are a safety item used whenever working on a vehicle or wherever there is concern of the vehicle rolling. Typical use of a chock is during maintenance that requires the vehicle to be raised on one end or when parking a larger vehicle on an incline. The exact size of chocks you may need depend upon your vehicle and your needs.

Identify Your Vehicle's Needs

Step 1

Measure the height of your tire. A wheel chock is best sized according to the size of the tire and should be approximately 1/4th the height of the tire. If your tire is 36 inches in height, your wheel chock should be around 9 inches high and fit snugly beneath the tire.

Step 2

Look at the grade of the terrain the vehicle is to be placed upon. Grade refers to the angle of the ground. While a chock needs to be approximately 1/4th the height of the tire, you may require more than one chock. If you are on a 30 percent grade--which is approximately the angle of stairs, you will want your chocks to be sufficiently large enough to hold your vehicle while in neutral and you will want a minimum of two chocks.

Step 3

Look at your owner's manual. For larger vehicles such as RVs and tractor-trailers, the vehicle's manual may describe a need to chock both the front and rear of the tires for reasons of potential brake failure. Even if you are parked on level ground, there is still danger of a vehicle rolling.

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