Bolt Pattern Basics
Every vehicle rolls off the assembly line with wheels designed to its exact specs, which means there’s no such thing as a one-size-fits-all rim. So, if you’re in the market for some new ones, you’ll first need to know a few measurements — the desired diameter of your new wheels, the desired width and offset, and the specific bolt pattern required.
In this article, we’ll focus on the bolt, or lug, pattern. This pattern is comprised of two numbers. The first indicates how many bolt holes are on the wheel, while the second describes how far apart the bolt holes are from one another across the diameter of the wheel. For example, “4 x 100mm” describes a wheel with four holes total, spaced 100mm across from one another when measuring from the center of each lughole.
Measuring Your Bolt Pattern
Wheels with 4-, 6- and 8-bolt patterns are measured from the center of one lughole to the center of the opposite hole. Wheels with a 5-bolt pattern are measured using the diameter of a circle that crosses through the center of the lugholes. Measuring a 5-bolt pattern is very difficult and not recommended to confirm wheel fitment without using a bolt pattern gauge. Below are examples of measuring 4-, 5-, 6- and 8-lug wheels.
Millimeters vs. Inches
Both millimeters and inches are used to measure your wheel bolt pattern, sometimes interchangeably. Since a few millimeters can mean the difference between a wheel that fits your car and one that doesn’t, it’s essential to be as exact as possible when determining your wheel lug pattern. Looking up your specific application online is usually the easiest method, but physical measurement always adds piece of mind. Investing in a bolt pattern gauge makes the process as simple and accurate as possible. Many wheels might only be listed in mm, while others exclusively in inches.
Your wheel might have a measurement of 4 x 114.3mm, with an equivalent measurement in inches of 4 x 4.5”, for example. Some sites only list one method of measurement, but not both, so knowing your bolt pattern equivalent makes it easier to shop for all the possible wheels that fit your vehicle. See below for a complete bolt pattern conversion chart for millimeters to inches, and vice versa.
Bolt Pattern Conversion Chart
Although incomplete (in the sense that there are far more measurements than presented), the conversion chart below offers accurate conversions, in case you’re having some trouble. We’ve got SAE to Metric, and Metric back to SAE.
Bolt Pattern Guide
A common example of a bolt pattern measurement is 4 x 100mm or 4 x 3.94”. While the second number in these measurements may look hugely different, the only difference is the use of millimeters vs. inches. This can be confirmed by the basic conversion factor: 1 inch = 25.4 millimeters.
The first number in a bolt pattern measurement — e.g., the “4” in “4 x 100mm” or the “5” in “5 x 4.5” represents the number of bolt and lugholes in each wheel. The most common lughole numbers are 4 or 5, which are typically used for sedans or coupes, while larger vehicles like SUVs and trucks generally have bolt counts of 6, 7 or 8.
The second number of a bolt pattern measurement represents the bolt circle diameter or BCD (which is the same as PCD or Pitch Circle Diameter). The BCD figure is measured by connecting the dots created by a wheel’s lugholes to create a perfect circle. The circle must pass perfectly through the center of each bolt or lughole for the measurement to be accurate. Once the circle is drawn, real or imaginary, you measure the diameter of the circle. The figure derived from this measurement is the bolt circle diameter, which is the key measurement in a wheel bolt pattern. In simple terms, it’s the distance from the center of one lughole to center of the other (most opposite lughole), measuring across the center of the wheel. The exception being a 5-lug pattern, which varies only slightly.
If you take one thing away from this article, take this — that even the slightest discrepancy in measurements can mean the difference between a sweet upgrade and a serious dilemma. Consult our handy lug pattern chart to make sure you have the process down pat, and take advantage of our lug pattern conversion chart to keep your math to a minimum. Once you’ve got the right set of numbers, AutoAnything has an incredible selection of wheels and lug nuts in varying sizes, styles and materials to choose from.