Getting the right bolt pattern measurement is very important, if you plan on purchasing aftermarket rims, since only one size bolt pattern will fit for each particular car. To measure an automotive rim, you must first remove the tire. Any measuring device that uses both inches and millimeters will work fine. Always remember to measure twice to verify that you have measured properly.
Measure the bolt pattern on the rim. For a wheel with an even number of lug nuts, measure from the middle of one lug nut to the middle of the third consecutive lug nut. For wheels with an odd number of lug nuts, measure from the middle of one lug nut to the middle of the opposite lug nut.
2
Place the rim on a flat surface. The diameter of the rim is the distance between the upper and lower bead seat. The bead seat, according to 1010Tires.com, is the edge of the rim that creates a seal between the wheel and the tire. Measure the distance between these two bead seats to determine the diameter measurement.
3
Place the rim in an upright position. The width of the rim is the space between the two bead seats that would normally be covered by a tire. Measure this distance between the two bead seats to determine the width measurement.
4
Write down the results of all the measurements. Bolt patterns are written as lug nuts times the distance between lug nuts. On a rim with six lug nuts and a distance of 135 millimeters between lug nuts, the measurement would be 6 x 135 mm. The width and diameter of the rim are written as width times diameter, so for a rim with a 17 inch diameter and an 8 inch width, your measurement would be 8 x 17 inches.
