That article wasn't thought out very well. They state that the overall diameter of the tire was taller with the 18" wheel which affected the overall gearing, which I think would hurt a lower powered car a bunch. So the diameter negated the lower weight of the 18" wheel/tire combo. I'm surprised that the author made such a basic mistake when setting up this comparison. When I went from a 17" wheel/tire combo to 18", the 18" combo was either the same or lighter than the 17" tires I had on the car before.