There is a button that can be selected from the setup screen called tire calabration. The Nav book has one small paragraph about changing tires.The button appears it should not be pushed until you change tire. Anyone know what happens when the "change tire" button is selected? I am not going to use OEM as there are much better tires out there that overall will be better for the car. Some of the replacement tire have rev per mile ranging from 890 to 903. OEM is 902. Was told to keep rev per mile close to tires chosen by Toyota, as that is what the speedometer and odometer are calabrated on(902). But there is this button >on the dashboard>menu>setup>calabration. After pressing calabaration there are two choices adjust position(and that is at the top of the screen) and at the botton is it says"change tires" press after changing tires..........What does this mean?