If the gryphon can't change that then the only option is you might have to have the dealership reflash it. If you look around you might be able to find a OBDII tool to recalibrate for bigger tires. I think I remember seeing something that can change that but I dont know what it will do with the tune. You can use the MPH parameter on the screen for your MPH reading but I'm not sure about the odometer.
