Don't know about the wheel fitting the bike but the 190 is the right tire for the 6". A 180 on that wheel would be too flattened out or something. The sidewalls would be straight up and down. Kinda similar, my SS came with a 170 on a 5.5" and it sucked. I continuously ran out of tire in the curves. hated that feeling. And, on a personal note, I wouldn't like the looks of a 180 on a 6". If you're worried about the handling, theoretically, a 180 on a 5.5" and a 190 on a 6" should be pretty much a spot on comparison as far as turn in.