2015F150Guy

I've read the guides, i'm just not having any luck.. Anybody in Colorado willing to meet up?

Bonus : Anyone know of any good spots for mudding in central or southern Colorado?

Summers22

iTrader: (2)

I will be honest, I am having a hard time with that as well. I am well versed in Forscan. But calculating tire size to the correct code to enter has me wondering......not even sure if changing it would make a difference for me. I went to a 275/60/20 from stock 275/55/20. Speedo is off 1-2 mph according to GPS.

maco

Don't really know what this means....except a trend maybe??....
I have reprogramed (thru the dealer a ) over the years an 02/07/10 & an 11.....
I basically have changed usually either 1 tire size up or & also P metric to LT tires with a 1 size difference. 18'' to 17'' etc.............Everything comes back 2 mpg SHORT.....(in my case 1.7km short in 100km)....
I have read in these forums 2-3 times the same thing where an op had his his truck in for a recalculation of the computer to facilitate a tire size change (usually 1 tire size) & it is out exactly what you say ....2mpg !!

Double Haul

Hypertech, Rough Country, etc make calibrators for sale for about $140-150. Probably about the same cost as driving up to CO all in and you can adjust it for any future changes. Just thinking out loud here

2015F150Guy

Yeah, for whatever reason I can't seem to figure it out on my own. Dealer doesn't even believe it's possible to reprogram (idiots). Gps says i'm much more off than you are lol, but i've got larger tires.

2017bluetruck

I used this online active calculator to find the code to enter. Got my truck to within 1/2 mph at 50 mph. Checked it against several different GPS units. KM

Forscan tire diameter calculator

Found in this thread, Correct your speedometer error - no flash or tune required