1 Answer

From Wiki:  For a 4- or 6-bolt wheel, this measurement is merely the distance between the center of two diametrically opposite bolts. In the 4-bolt picture to the right, this would be the distance between holes #1 and #4, for example.

Some basic geometry is needed to find the center of a 5-bolt pattern. In practice, the BCD can be found by multiplying the center distance between any two adjacent holes by 1.701.

[show]BCD geometry of 5-bolt pattern

Generally, the BCD b can be calculated for any wheel from the number of bolts n and the center distance d between two adjacent bolts as: .

A far easier way, using less math, is to take calipers and measure the hole size in the center of the wheel (note this dimension). Next measure the distance between the edge of the center hole and the center of one stud. Double this measurement and add it to the first. Job done! This method works with any number of studs.