I'm curious as well with the recent discussion between the tire calculator advocates vs real-world tire selectors.
I brought this point up a couple weeks ago to a tire calculator advocate stating that if it was that important to maintain wheel size why did Ford change tire sizes resulting in a different overall diameter?
Knowing what I have seen from from Ford - no intermittent wipers on SVT, non-SVT radiators on SVTs, etc. I would be shocked if they actually spent the money to recalibrate the speedometer and odometer.
