# How to Measure Center Bore

by C.L. Rease
4 wheel drive image by Canakris from Fotolia.com

The machined center bore of a wheel determines the type of vehicle a wheel will fit. A center bore not matched to a vehicle hub will cause vibration. The vibration will make the vehicle uncontrollable at high speed. Wheel manufacturers enlarge their wheel's center bore to accommodate a wide range of vehicle types. Determining the center bore of your wheels will determine whether you require a hub ring to increase the strength of the wheel and reduce vibrations from the installed wheels.

## Step 1

Set a wheel, hub-side up, on a firm flat surface.

## Step 2

Press the zero end of a steel rule against one side of the center bore.

## Step 3

Set one side of a 4-inch combination square blade against the inside edge of the center bore, opposite the zero end of the steel rule.

## Step 4

Read the number of the steel rule aligned with the side of the combination square blade set against the center bore. That number designates the diameter of the center bore.

## Step 5

Convert the fractional portion of the measurement to decimals. Enter the non-whole number of the measurement into a calculator. Divide the top number and bottom numbers of the fraction to find the fraction's decimal value. For example, the fraction 3/16 would be three divided by sixteen for a value of 0.1875. Rounding the number to the nearest hundredth 0.19 shows the decimal equivalent of 3/16 inch.