I purchased a 2013 FX4 about a month ago. Since then I have installed a 2" level kit and some 275/65 R20 tires and put them on factory rims. I have never really looked at the navigation screen until the other day and I noticed that it was displaying me driving about 100 meters off of the actual highway I was travelling on. Since then I have paid more attention and the vehicle icon is constantly off of the road I am travelling on and usually several blocks back from my current position. I took it to the dealer and they said is was because of the tire size change. They said they could not adjust the computer to correct for the size of tires I chose as they are outside of their calibration range. My question is what does the tire size have to do with my position that is calculated based of off signals from satellites?? Why would the navigation system even care if I have tires on the truck? As of right now I can't use the nav system to direct me anywhere because it has no idea of where I really am. Ay help regarding this problem would be much appreciated.