what number is the pulse asking for I am running 315/75/16 on my truck and stock was 245/75/16. It has a number like 120.6 or something like that for stock

I am wanting to correct my tire size but just got this thing and trying to learn all the in's and out's

 

Take some chalk, mark the tire at the very bottom on the tire itself. Also mark the cement at the same spot. Start the truck up, put it in gear, and move forward. Have someone outside of the truck watch until the chalk mark on the tire makes one revolution. At that point, stop the truck, and mark the cement. Measure from chalk mark to chalk mark and enter that measurement into the adrenaline, this will give you you're corrected speed. If i'm wrong, someone else will chime in.

Bryan