I have a 2006 F150 XLT that came with 255/65/17 's. I have since upgraded to the FX4 wheels 275/55/20. I know the speedometer is off because the tires are larger. Can this be adjusted? I seem to be getting conflicting stories from different dealers. Some say yes, some say no, some say maybe. The maybe's are saying that they can only be adjusted a couple of sizes, whatever that means, and that my change may be too large. Some of you must have done this. Any Help?

 

I had the dealership reprogram the PCM from my stock 275/45/20 tires to 275/55/20 with no problems. It goes back when I had it done, but it was reasonable. Good luck!
RH