In my case my truck came with 265-60-18's and i went with a 275-55-20 wich is a pretty standard size these days, could ford recalibrate my truck since they sell alot of trucks with this tire size standard? My speedo is off about 3mph, i know when my truck says im going 72mph im right around 75 on gps.

 

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Raising this one from the dead. Are there any calibrator on the market that don't change the tuning of the vehicle? I don't want to mess with anything related to the performance of the truck, just want my speedo/odo to be correct.

 

I have the Hypertech Speedometer calibrator and have been very happy with it. Found it on sale for about $180 awhile back and just used it this past weekend to adjust my speedometer when I got new tires (32s to 33s). It just does speedometer calibration, viewing and clearing trouble codes, and adjusting rear gear ratio, nothing crazy, but exactly what I was looking for. Hope this helps.