[Pantah]

Originally Posted by dad2bike

I found this. http://www.ehow.com/how_4841621_dete...tire-size.html
It seems a 120/100 would be 120mm tall and a 140/80 would be 112mm tall.
I guess the 140/80 would shorter.
I guess I could go for 100/100. That would surely give clearance.

Yes your are correst. The first number is the width and the second number is the height expressed as an aspect ratio of the width.

90/90/21 says the width is 90 and the height is 90% of the width.

At least that is what the tire section of motorcycle-superstore.com says.