I read the tech article on how to calibrate the speedo, but it seems it only shows the formula for calculating tire size changes. What about for gearing changes? Right now my truck has 3.2x's in it, and tomorrow I'm installing 3.73's. How do I calibrate it for that?

 

Nevermind...I found my answer.

 

And what would the formula be for calibrating for tire size?

 

there is an article here, run a search for it and you should be able to find it.