I'm interested in doing something different with my bob. Matching the wheel diameter, but instead of going smaller in front, was thinking about going larger in the rear. Has anyone seen pix of how this turns out?

 

Well, it would make your motorcycle look more like a bicycle. If I were you, I'd go smaller diameter on the back, to a 16" wheel, make it look more like a Harley.

 

Its already a 16. I was looking for a way to fill the fender without lowering it. I already drag it in corners everywhere I go at stock ride height.

 

You should poke around on some of the manufacturers web sites to see if such a tire even exists. I don't know if there is a 19" tire out there designed for rear tire usage. Even at that, the OD of the tire may not be all that much different than the 16" tire / wheel combo. It might be easier and cheaper, and certainly safer to buy some sort of crotch rocket that will suit your style.