I'm looking for tires for my truck to get it into working order. However I only looked at the size it has on now. If I remember correctly, the speedometer was off a bit but I have no way of knowing if it is because of the wheels and tires or because my speedometer needs calibrating. I don't have the owner's manual and the haynes manual is useless in this (if not altogether). Also, I need to find out how to calibrate the speedometer myself as well.