Go here to learn the correct way to use the method in your picture; Measuring Bolt Patterns - How to Measure Your Rim's Bolt Pattern , even then it doesn't work perfectly. We agree they are Buick wheels, GM didn't use a 4.5" bolt pattern when these wheels were used, they used 4.75", so even though I didn't use a ruler I feel confident in saying they are 4.75" bolt pattern. Buick did have a wheel similar to these, but not exactly the same, that has a 5" pattern. Cheers, Mike