90/90 18 inch tyre instead of 90/100 18 inch.

[Next edition]

The figure after the slash show tire height relative to the width, which is the first number (in mm).

In other words 90/90 is a tire that's 90mm wide and 81mm high (90% of 90mm = 81mm), while 90/100 is again 90mm wide, but also 90mm high. And they both have inner radius of 18 inches (yeah, it's really nice how they mix up Metric and Imperial units!). Rim width does not play in this case.

I was kind of wanting to know how the rim width sizes measurements vary just so I can match up other brand tyres to ones that are similar to mine are,like would a kawasaki 90/90 18 inch tyre fit on a yamaha 18 inch rim for example or would they have different rim widths.