Width (130/90 16)
The first number in a tire size represents the nominal width (usually in millimeters). 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.
Aspect Ratio (130/90 16)
The aspect ratio indicates the height of the tire's cross-sectional profile. It is expressed as a percentage of the tire's width, so an aspect ratio of 55 means the tire's cross-section is 55% as high as it is wide.
Rim Size (130/90 16)
This number is the diameter of the rim on which the tire will fit. The number is expressed in inches.