Making sure your wheels fit properly starts with knowing you have the correct bolt circle size for the wheels. Most of the time this information is easily found for a car that’s using a stock rearend, but if there’s a custom or aftermarket rearend in play, and the car was purchased used you might not have that information. WELD Racing goes over some different ways how you can get the correct bolt circle measurement for your rearend in this video.
To get the most accurate and correct measurement for the bolt circle of a wheel you need to measure the studs on your axle ends. The studs need to be directly opposite of one another to ensure the bolt circle measurement is accurate. Obtaining this measurement should be done with a ruler or straightedge to give the most precise measurement. Using the bottom edges of the lugs provides the best point of reference to measure from so you don’t have to guess where the center of the lug is.
When a lug pattern is an even number, like a four, six, or eight lug-style, it’s easy to find the bolt circle measurement from center-to-center on opposite lugs. A five lug design is slightly more challenging, but can be done in a similar method to the even number lug design. You can measure from the two studs that are across from each other, and use the bottom edge again as your point of reference. After you take that measurement just add a quarter-inch to get the true size of the bolt circle that accounts for the distance difference.
This video from WELD Racing is packed with great info for measuring bolt circle, and is worth watching from start to finish if you need to order some new wheels without having the bolt circle size handy.