Something to consider; The larger diameter rear rim you use, the narrower the tire must be. I run an Avon supervenom 130/90 on a stock size 18" rim. You may be able to get away with a 140/80, but the taper of the swingarm gets very close to the shoulder of the tire.Also, if you ride hard enough, will the tire twist enough to make contact with the swingarm? I won't risk my hide to look cool with a fat rear. Wait... that doesn't sound good! Shiny side up, please.
This brings me around to what I've been thinking about lately- I want to have fatter tires on my CB550.. The reasoning being that the fatter the tire, the bigger contact patch. This would allow for more traction, and better stopping, etc. I just learned from reading here that you can't stuff a wider tire on the same size rim, as it doesn't work right. So, you need a wider rim to run a wider tire. And, if I want wider wheel/tire, I gotta use a smaller diameter, right?
So, what do you look for when you are computing everything to figure out what size rear wheel, tire, etc. to make/buy? If you get a smaller diameter, wider wheel (so you can run that wide tire), do you get a taller tire, so that ultimately you have the same ride height in the back (i.e., the outside diameter of the new wheel/tire is the same as the stock wheel/tire?)
Finally, how can you compute what size tire to put on a known size rim?
Jason