I changed to 315/30X18 tires on the rear, OD went from 26.1 to 25.5". In Navigator, Speedometer, parameters. The VSS config. window that opened had tire diameter and a "New" window, which I changed. The Diff. window had 1.000000 and a window for "New" I put in my ratio, 3.42. Is this correct? What about the "Adjust" "Save" and "Revert" buttons?? I clicked on save.