He built this box for my exact percentage it was off. So I'm sure you can get the correct gears to put in the box if you change tires again. He just had me go 40 on the gps & give him the indicated speed on the speedo, then the same at 50, & 60. Mine came out to a 1.25 increase. They offer other ratios that are more common for a little less money, but since mine wasn't a stocking item it cost a little more to build custom.
I'm very happy!!!