rear rim

[bubbajerr8]

whats the widest rear rimand tire i can stuff in gs11003 swingarm wanna make it look mean from behind thanks jerry

[TheCafeKid]

You can get a 4.5" rim in there, maybe even a 5" rim. But you can't run bias ply front tires with radial rear tires. So unless you plan on spending some dough upgrading the front end too, the widest GS rim you can put back there is 3.5 from an 1150. However a fat tire doesn't make the bike look any meaner to people who actually know how to ride in anything other than a straight line.
A fat rear tire slows turn in speed and makes for non linear handing if the front isn't proportionally as wide. Ie, sticking a 170 on the back with a 90 or 100 on the front will make it handle like crap.
It might look cool, but it sure won't ride cool.