Rim Width
   The width between the flanges of the wheel (the part the bead    of the tire touches).

Section Width
   The linear distance between the outside of the sidewalls of an    inflated tire without any load on it (this does not include any    sidewall decorations).

Section Height
   This is also known as the Aspect Ratio. This is figured on a    percentage of the section width. A tire size of 205/60R15    would have a section width of 205 millimeters and a section    height of 60 percent of 205 millimeters.