Determine the bolt pattern by the number of bolts and the bolt circle. To determine the bolt circle on wheels with an even number of bolt holes, measure center-to-center on bolt holes directly across from each other on the diameter (Example: 8 on 6-1/2 would mean 8 bolt holes with 6-1/2" center-to-center diameter). On odd number bolt wheels, measure any bolt hole center to the point halfway between bolt holes on the diameter (Example: 5 on 4-1/2 would mean 5 bolt holes with 4-1/2" measured to a point halfway between the opposite bolts).