2019 F250 Speedometer Recalibration for Larger Tires

[@armedprophet3321]

I believe anything 37 inches or bigger is not able to be programmed into the trucks system. There is an external device that you can get from Rough County that will allow you to correctly run any size tire.

[@timbo_slice4053]

I've not been able to program 37's with forscan. It throws a check engine light.

[@armedprophet3321]

@@timbo_slice4053 You are correct. Look up Rough Country speedometer calibrator.

[@Painfulwhale360]

@@timbo_slice4053did you reprogram the all the other modules?

[@mastern3825]

2476 millimeters equals 97.4 inches, which appears to be circumference of wheel. Divide circumference by pi, and you get a diameter of 31.02 inches.

[@CarShopTalk]

Sounds right. I think they’re actually like a 33.4 inch tire from the factory on that. You just have to play with it a little to get the speedometer correct

[@travistorres5891]

I have a 2018 Ford F-250 4WD 6.2 V8 with oem tire size 275/70/18 and I am installing 285/75/18 tires on the vehicle, do in need to do this and will it hurt the vehicle in any way if i don't?

[@CarShopTalk]

The oem tire you mentioned is a 33.5-inch diameter. The new tire is a 35-inch tire. The speedometer is going to be off, and the vehicle will seem a little more sluggish due to the perceived increased ratio with the new tires. The tall ratio does put more stress on the transmission and everything else, but people do it all the time without problems other than the speedometer being off.

[@traxxi2003]

How do you calculate the Hex-decimal number? And what is that last set of numbers again?

[@CarShopTalk]

There’s a formula for it, but there are so many free decimal to hexidecimal converters online I usually just Google it and use one of the top results. Just Google “Decimal to Hexadecimal converter”

[@jviel]

Will that adjust shift points, fuel economy numbers etc?

[@CarShopTalk]

Shift points no, fuel economy I would think yes.