Forscan adjustments for wheel/tire size?

[tls]

My 18" wheels with snow tires are just slightly smaller enough than the original 20" package on my Lariat that the speedometer difference is annoying. Is there an adjustment I can make in Forscan when swapping out the wheels?

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[ZheWiz]

There's a setting in the Body Control Module for your tire circumference in mm. The stock Lariat 20" tires have it set to 2547. To get the correct NEW size, calculate (or look up) the circumference of your tire in mm, multiply by .968 (because rolling circumference is slightly shorter) and enter that new number. Adjust as necessary, but that should get you REAL close...when I did that with my aftermarket 18's the speedo read 1 MPH low. close enough for me!

 

[tls]

What address is this setting at, and how is the number entered? Or are you using the other mode in Forscan? I'm leery of that because Googling around, I see a bunch of warnings that this is set at different locations and even in different modules for different F150 years, and I can't find a clear statement of which is the right module and address for the Lightning.

 

[ZheWiz]

It's not the "Hex" area that needs adjusting...it's the "English" section, so really easy to change. I don't remember exactly what it's called, only that you'll know it when you see it. If you scroll through the Body Control Module options, you'll see it. I'll have to do mine again in the spring when I change back to stock, but my memory isn't good enough to tell you much more than that.

 

[MountainAlive]

I’m going to be going from a 275/60/20 to a 275/70/18 for winter and the difference in circumference is like 12mm bigger so I’m not sure if I need to change anything? I think it would make my speedometer like 0.5mph off. But unsure if I’ll bother with forscan or not.

 

[potato]

I did the hex edit. Didn't look for any user friendly interface for it. Instructions here: https://www.f150lightningforum.com/...s-after-lift-and-bigger-tires.1058/post-19844

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