We have an 02 Dodge 2500 that we put slightly oversized tires on which put the speedometer off by about 2.5 mph according to my two GPS units used. I have a 04 Exp 4-wheel drive that I'm wondering how the addition of over oversized tires bothers all the computers. The truck has advancetrak(sp) which I assume also includes that infuriating traction control system. As a side rant... As a person that is still used to using the foot feed to control the vehicle, my blood pressure rises when that dad-burned traction management system shuts off engine power and applies the brakes when I need the tire speed the most! Pressing the delicate little button to shut it off shows that it turns off but nothing changes. So stuck I get on wet grass in the hay field. And that's in straight 4H. Anyway, this question is about the speed sensors not my rant on the traction control. How is the engine management systems reprogrammed for larger tires and can it be done without sending half a weeks wages home with a dealer mechanic?