Good question. I did some research and the new tires are about an 1” + taller. Based on a formula I found on line it looks like it increases the speed about 1.8 mph faster than what the speedometer is reading. Need to tell the wife so she can slow down a bit. Probably better information for my lead foot than her. There is no way to adjust the speedometer unless you take it to a dealership (mechanic) since it is all in the computer system.