If its a TrailTek don't get to excited . I have one and set it exactly to my tire size and all was cool. I could hit 80 in dirt ( fair amount of mods, but needing a rebuild). Then I moddit it and rebuild, up a tooth, & hit 107 mph - sh*t my pants. Got a GPS and the fun was over best is about 90 mph. I think it just goes nuts sometimes or can't go that fast or something, recalibration to a bigger tire is in order. Anyway I still like it, when I'm 1/2 way out of gas is a good thing to know!
Enjoy!!!