In the owner's manual for my '95, it shows that the standard tire size is 235-75's with the option for 31-10.5. I would like to change to the smaller "and cheaper" tires, but what will that do to my speed-o-meter? What do they do at the factory, change the speed-o-meter gear? If so, does anyone know the part #. I'm new to your forum having just purchased my Pathfinder. Can use your help.