Measure the bolt pattern for custom rims by first determining the number of bolts on the wheel. For wheels with four, six or eight bolts, measure the distance between two bolts on opposite ends of the rim from center to center. For wheels with five or seven bolts, the most accurate method is to use a bolt pattern gauge.
To measure the bolt pattern on a wheel with an even number of bolts, place one end of a tape measure on the center of a bolt and extend it to the center of the bolt directly across from it in a straight line. While the most accurate way to measure the bolt pattern on a tire with an odd number of bolts is to use a special measuring tool known as a bolt gauge, it is possible to estimate the distance. One method involves measuring from the center of one bolt to the bottom of the area between the two bolts directly across from it.
The bolt pattern of a tire refers to the diameter of the circle that forms from the bolts on the wheel. These wheel bolts let the owner of the vehicle secure the rim onto the wheel, holding it in place while the car is in motion. As each wheel needs to have a rim with an exact matching size to avoid safety concerns, it is necessary to measure the bolt pattern to create a custom rim.