The linear distance between the outside of the sidewalls of an inflated car tyre without any load on it (this does not include any sidewall decorations).
This is also known as the Section Height. This is the percentage of the section width. A tyre size of 205/60R15 would have a section width of 205 millimeters and a section height of 60 percent of 205 millimeters.
The width between the flanges of the wheel (the part the bead of the tyre touches).