Our '02 has the 265/70-16 aluminum wheels with worn out Firestone Wilderness LE tires. I'm thinking that since 17" were an option that would be a nice appearance upgrade and keep the 16" for dedicated snow tires. However, I don't want to introduce speedometer and odometer error by going to the optional 265/70-17 wheel/tire combos. How do the factory guys do this? is there some speedo electronic setting that is changed via a programmer? Or is it within the speedo error margin anyway? According to the miata.net tire size calculator, the optional tire size would cause the speedo reading to be 3.3% too slow, or at indicated speed of 60 mph the actual speed is 62 mph. Your thoughts?