Speedo out??

[54D18]

I changed tires from 255 to 245 on my 06 f150 and the speedo was out, I had the dealer reprogram and it was still out by 5 km/hr.
I am installing an Edge Evolution this week to optimize for towing, I'll be programming the tire size at the same time.
I thought I had read that the shift points are determined by speed, if this is true, then it would have been trying to shift to early as my speedo read 5 km more than actual speed.

Sent from my iPhone using F150 App

[54D18]

I was able to adjust the speedo in the edge, not exactly accurate at lower speeds, but bang on at the highway speeds.

Sent from my iPhone using F150 App

[Raptor05121]

shift points are determined by a variety of factors, throttle position, transmission load, converter state, etc. By stock, your speedo reads 2-3mph slow from the factory at 60mph