unprogrammed my truck and am putting tunes back in but instead of playing around with the tire revs (speedo cali) what have you guys used running 275x55x20 pirelli atr's? i know the equation but then you start adding for the squish or what ever you call it.

 

Actually you subtract the squish factor as a percentage (anywhere where from 2-5%) by multiplying the circumference by .98-.95.

The factor will depend on the tire pressure, temperature, and tire age. Most people start at 2% and then confirm with a timed mile or GPS.

https://www.f150online.com/forums/ch...ture-size.html

https://www.f150online.com/forums/ch...zing-edge.html

https://www.f150online.com/forums/ch...sh-factor.html

https://www.f150online.com/forums/ch...ires-size.html

 

I think the Gryphon equation does deduct 3% for squish. The Edge equation does not, and you have to deduct it..

 

i did 2469 does that sound about right and when my custom tunes came they had wrong gear ratio no biggy to change i just thought that was done in with the tunes

 

Yep - that's 3% for a 275/55R20.

 

Did you go into custom options to verifiy?
If you opened custom options to verify your TS+GR it probably gave you arbitrary values instead of the values that were built into the calibration.
Or did you verify with a gps?
I have the same TS and tires, the value I used is 2479.

 

IF you told Bill your TS and GR when you requested your tunes, I'm sure they are built in to the tunes and you should not have to "adjust" them.

But IF, you open the Custom Options menu and "look" at the values for TS and GR, they will very likely be wrong and you WILL have to adjust them. The programmer "loads" arbitrary values when you open that menu, regardless of what's in the tune. The fix is to bypass the ""Create Custom Tune" step, then, the values that are in the tune will be used.

P.S. - There's really NO way for you to see that the wrong GR was in your tunes. You do not have access to that information.

Since you have a Gryphon, please read through this Q&A about using the Custom Options menu: Q&A About Custom Options

- Jack