Hey J, Heres a pic of my Rubi with the 26 Bear Claws, I did alot of research and most people said the 27's rub very slightly when the bike is stock. I am the type that doesnt want any rubbing at all, even a little is too much for me and I dont want a lift so I was ready to put 25's back on. Anyway I finally bought the 26's and they fit perfectly. For my liking I really wanted to stay under 10" on the fronts to keep steering as easy as possible, and by pure luck the tires line up perfectly, measuring outside to outside they are identical the 26x9x12 front and 26x12x12 rear keep the width of the tires the same. My concern was the fronts sticking out more than the rears and it looking funny. I love the way it looks. as far as fitting the rims, you'll have no problem either way, the 12's fit the stock rims fine. Whatever you decide good luck, I think you'll like the tire, its very early for me but so far I love them, now if we got some snow.....
Ron