CST for your 1987 Kawasaki KX80G

Width is measured in a straight line from the furthest point on one sidewall, across the tread, to the furthest point on the opposite sidewall.

The aspect ratio is the height of the tire sidewall. A smaller number means a lower profile, and the height-to-width ratio is shown as a percent.

Rim diameter is the diameter of the rim/wheel on which the tire will be mounted, in inches.