I put 285 series tires on my '06 K2500. This has messed up my spedometer quite a bit. When the truck spedo says 70 my GPS is saying 76-77. I know I can fix this by getting a Hypertech (or other) programmer and resetting for a differant tire size. I have also been told the dealer can do this as well. Here is my real question, though. Is this affecting the odometer. I mean, if it thinks its going slower than it really is, is it recording less miles? I would imagine after a couple years this would make a pretty big differance in what the odometer says, VS the trucks 'Actual milage' ? Just curious.