What is the early Bronco wheel bolt pattern?

The early Bronco wheel bolt pattern is 5 on 5.5" (also written 5x5.5"). If you are looking at metric wheels, you can also use 5 x 139.7 mm wheels on a 66-77 Ford Bronco. These two bolt patterns are interchangeable. Any wheel with a 5 lug pattern and bolt circle diameter of 5.5" (139.7 mm) will bolt up to a classic Ford Bronco. There are other considerations as well when selecting wheels for your Bronco or other vehicle including the offset, backspace, rim diameter and width to name a few. The bolt pattern may also be referred to as the wheel lug pattern.

How do you measure wheel bolt patterns?

Once you understand the basics, measuring the wheel bolt pattern on your vehicle is straightforward. The bolt pattern is simply the number of bolt holes on the wheel by the diameter of the bolt circle. The bolt holes on every automotive wheel should be evenly spaced, so having just the number of bolts and circle diameter is adequate for identifying the wheel 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.

Measuring the PCD of a wheel Measuring the bolt circle is often the confusing part of identifying a vehicles wheel lug pattern. The measurement you are looking for is called the Pitch Circle Diameter (PCD). It is usually expressed in millimeters, but can sometimes be expressed in inches as well. For wheels with even amounts of bolts such as 4-bolt or 6-bolt wheel patterns, the PCD measurement is straightforward. Just measure the distance between the center of two diametrically opposite bolts.

Measuring a wheel with an odd number of bolts, most commonly a 5-bolt pattern, requires a bit more science. 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, and then multiply this result using a multiplier of 1.05 to find your bolt circle diameter.

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" whereas an early Bronco wheel will have a PCD of 5.5" or 139.7 mm making it 5 on 5.5" (5x139.7 mm)