To find the BCD, which is the diameter of a circle whose circumference runs through the center of each lug hole on a wheel, start by detaching the wheel from the vehicle. Label the studs on the wheel successively as A, B, C and D if the wheel has four studs, and add studs E and F if the wheel has five or six studs. Using the measuring tape, measure the distance between the centers of the studs A and C for a four- or five-bolt wheel, and the distance between the centers of studs A and D for a six-bolt wheel. You may repeat the measurement for accuracy.
Once you determine that the BCD measurement is accurate, count the number of bolts on the wheel, and add the number to the BCD to get the lug pattern. For instance, if the BCD is 4.8 inches, the lug patterns for four- and five-bolt wheels are 4 x 4.8 inches and 5 x 4.8 inches respectively. The lug pattern is 6 x 4.8 inches if it is a six-bolt wheel.Learn more about Tires, Rims & Wheels