There are four components to specify the measurement of motorcycle tyres. They are rim diameter, tyre width, height and aspect ratio. Rim diameter is the inner diameter of the tyre measured from the edge that meets the rim when the tyre is installed. The width is the distance between the two ends of the widest part of the tyre. If the tyre width is more, it will improve the handling but is bad for mileage. Another thing is the aspect ratio of the tyre. The height is the thickness of the tyre or the difference between the outer and inner diameter. And the height to width ratio is the aspect ratio.