How To Measure Bolt Patterns
Item #: Bolt_Patterns
The bolt pattern is merely the number of bolts on the wheel. As the bolts will be evenly spaced, the number determines the bolt pattern. The bolt circle is the circle determined by the positions of the bolts; the center of every bolt lies on the circumference of the bolt circle.
The important measurement is the "pitch circle diameter" (PCD), usually expressed in millimeters, although inches are often used. For a 4- or 6-bolt car, this measurement is merely the distance between the center of two diametrically opposite bolts.
If your wheel has a 5-bolt pattern, measure from the BACK of one bolt hole to the center of the second bolt hole as shown in the diagram. You can also measure from the CENTER of one bolt hole to the CENTER of the third hole using a multiplier of 1.05 to find your bolt circle.
A wheel with a 5 bolt pattern that has a pitch circle diameter of 4 1/2" will be defined as being a 5 on 4.5"
Hope this helps you with the measurements.