Some excerpts from posts over there at superhawkforum.com :
"Most 190's are meant for 6 inch rims. The VTR has a 5.5. You have to pinch the beads much tighter to fit. If you mount your own tires by hand like I do, you won't like this side effect at all.
The intended profile will change giving you a smaller contact patch than if on a 6 inch. This also slows down your handling. The tire won't look as wide as it could which is the most common (if unstated) reason for going with "meatier" tires but yes it will look wider than the stock 180. Your unsprung mass is increased somewhat which theoretically slows down your suspension reactions."
"those whose bikes come with 190s change them to 180 usually at the first tire change time, to get faster turning response.
Other than visual effects, 190s do not provide any advantage over 180s, so why bother??"
"Mine came with the 190 and i changed it first chance i got to the 180. Its hard to believe that a small change like that can make a huge change in the way the bike handles. Another plus is the smaller tire is less expensive."
"After I picked up a Key, (yes an ordinary house key) in the rear tire, I had a 190/50 put on, (emergency only tire in the county away from home), the bike tended to fall into corners and wore out extremely quickly. Apparently the contact patch is greatly reduced when upright. I switched back after I wore it out, had to be only about 1800 miles. that was with a Metzeler Sportec M-1. By the way, a great tire, but they wear too fast."
And last but not least, here is some info from Sport Rider on it: