I replaced my Transforce AT 265/70R17s with Transforce AT 285/60R20s, There were no fitment issues, the new tire is 4.71 inches in circumference larger. This amounts to 8/10 of a football field per mile, or 237 feet/5280 feet increase in distance traveled per mile indicated. GPS comparisons confirm this.
I have not noticed any problem in shift points, towing or not towing. And my antilocks are working just fine. It would not seem that 237 feet per 5280 feet would affect the anti lock, traction control or shift points. However this topic is discussed on other forums with mixed opinions. Many of their problems extend from the addition of very large tires. They do have fitment, sensor, and performance issues. I dont know if we are really talking about the same level of modification as they are.
BTW, I talked to my service department about this. They told me about the programmers. But they also told me that RAM will know that I made the change and that it would affect my warranty if the change caused a problem. He also told me that it was not a real programing change, it was just a way to fool the onboard computer into displaying the correct speedometer information. Since my speedometer is virtually accurate to about 60 MPH and shows a 3.5 mph spread at 70 to 75 mph, I have decided to live with it.
If I would have installed any of the 3750 lb tires at 34.1 inches, my tire diameter would have increased 2.2 inches instead of 1.5 inches. This was not an acceptable increase for me. I would have liked to have the 3750 lb tire, but 3640 is ok.
