2015 f-250 new tire size(37") calibration

[dgmartens]

I have a 2015 Ford F-250, 6.7 L and factory tire size is 275/65/R20. This is the largest tire size you can go to with this year. So, I put on 37/12.50/R20 and my speed was 2.5 miles per hour less. The only remedy I found was to buy a Rough Country Inline Speedometer Calibration Kit. On set up of new inline speedometer calibration, I put in new tire size 37/12.50/R20, and it read 2.5 mph more, so I reprogrammed it using actual tire diameter which was 35.5 inches. After inserting 35.5 inches into new tire size and taking it for a test drive, it was right on. I purchased the Rough Country at 4-Wheel Parts for $169. Problem solved!

[JRCustomCar]

You can actually enter values in Forscan to compensate for larger tires. I haven’t done it (mine is accurate) but there was a member on 6.7 Powerstroke facebook group that figured out the tables, sadly he passed away last year.

[JRCustomCar]

HOW TO CALIBRATE YOUR LIE-O-METER

I keep hearing people complain about how far off their mpg display is. They always express frustration - as if it's Ford's fault and some sort of grand conspiracy.



It's not.



The mpg display is simply a calculation based on miles traveled divided by fuel used. Math doesn't lie... So if it's inaccurate, then one (or both) of the pieces of info it's getting is wrong. Usually it's the miles traveled, because people commonly change tire size without telling the mpg display... And since the truck calculates distance based on tire rotations, any change in tire brand, model, pressure, or size is going to change that reading.



Here's the short version of how to do that with any Ford vehicle made in the past decade or two:



1. Use a GPS (Waze, Google Maps, any speedometer app) to figure out how far your speedometer is off. Set the speedo to 60 and record what your GPS says.



2. Download Forscan from Forscan.org. It'll require an OBDII reader ($50 Amazon), a Windows-based laptop, and some reading on how to operate. If you can't do this, get a friend to.



3. Open box 726-12-01 in the BdyCM tab and write down the alphanumeric digits in the middle field.



4. Reply to this post with your two speeds and the alphanumeric digits.



5. I will send you back new alphanumeric digits to put in that field. Save/write them to the truck's system.



6. Enjoy an accurate speedo, odometer, and truth-o-meter.



If your truth-o-meter is still incorrect, then shoot me a PM and we'll calibrate your fuel tank size as well. FWIW, 2011-2016 long beds have a 37.5 gallon tank, not a 35 gallon tank... So if you've changed that with EZ Lynk, you may want to change it back.



PFA.

[magneticeagle]

Is there a hex code or circumference in mm that actually works without triggering CEL?

[jonnydz]

Hello. I am responding to your post for the correct info for fixing my Speedo being off.
At 60mph my gps is reading 64mph
726-12-01 middle box reads 0A47
Thanks in advance

[jonnydz]

Anyone able to help here.

[jimeg]

On my 2015 F250 6.7 I find that 726-45-01 is the place for the tire change. Works better but still 2 tenths off on odomter and speedo is 1, maybe 2 low

[jimeg]

Anyone able to help here.

I can try to help, what is it you need'