Will 18' wheels and tires fit on an R6? If not will a 190 tire fit on the stock wheel?

best talking to a tire specialist for that stuff....maybe one that does a lot of performance stuff they will know if it can or cant based upon what you have and etc, they can even take measurements and tell you how big you can go

Okay it depends on what type of wheel and tire you want to use. Where are the 18s coming from? Are they a sport bike or wire wheels or dirts? whats the deal?
Also sticking with the 17s most major tire manufacturers make incredible tires in 17s. You can range from a Michelin Macaderma that gets like 15k miles of wear and crappy traction to a Pirelli Supercorsa Super Soft that gets 100 miles of wear and so much traction you could peel asphault. So I'm confused why you're switching.
Also 190s you have to check what aspect you're using 190/50, 190/55, or 190/60. The tread will fit width wise. You're only talking an additional 5 mm on each side. However when you multiply that into the aspect ratio, which gives you height, you may run into problems. I know the new honda 1000rrs that won't allow the taller tires unless you use a chain 1 link too long so you can adjust it further out.

Again confused why the switch. A 180 gives you a nice angle at full lean so you still have a good contact patch. The 190 will have a different shaped crown and will give you undesirable handling. Example most guys that run RC51s start with stock 190 rears and switch down to the 180s for a wider selection of tire choices plus improved handling. Check out sportrider.com they have a comparison on tire shape on size under the tech section.
Hardcore racers will switch down to 16.5 inch rims so they can get better slicks, but I haven't come across anybody that switches up to 18s.
http://www.sportrider.com/tech/tires/146_0206_size

Again I am confused why you would want these changes. If you go to an 18" wheel you will screw up all the steering geometry of the bike. Because the wheel wouldn't be turning as fast you would lose the gyroscopic stability in the corners and the flickability of the bike. Also going to a 190 tire you would screw up the cornering of an R6. The only real mods you need to do on an R6 is to change the Dunslops to a 70 section tire ie Diablo's and set the sag on the bike. Just my views.

Nick

Thanks...I'll stick with the 17's, as not to srew things up. I would like to change to chrome or alloy wheels...any suggestions?