I would like to replace my front drum brakes with this kit from Wilwood. I currently have ralley wheels and wnated to know what the minimum wheel size that would fit over the rotors. I read the addembly instructions and measured my wheels, its VERY close. The instructions indicate 12.92" and I have a bit more than 13" but the wheel steps in toward the mounting surface. Also, forgive my ignorance, how do you measure the wheel to determine its size (diameter and width?).