Speedometer calibration 03' F350 7.3...7170

Hey guys, I just bought a Predator from an online dealer partly because he assured me that I could calibrate the speedometer by changing the tire size in the pcm by using this unit. It seems by reading some of the forum posts the only thing I can do is change the shift points for better response (the problem is in the abs???), but that there isn't much the predator can do to help me with the speedo/odo problem. I went from stock 265/75/r16 to 315/70/r17. I think by the time I hit 70 on the highway I'm really doing more like 76/77mph. If there is anything you can do to help it would be greatly appreciated.

[mikel]

Correct, the U7170 cant correct the speedo, as that is done through the ABS module, rather than the PCM.