To each his own ...but I think that since Honda engineered this bike and it came stock with 140/70/17's on the rear myself I plan to stick to stock sizes. Do you guys realize that in Motto GP the 250's are fitted with narrower tires (with alot more power) than our 300's have. This is by design to help with the bikes handling. Like I said ..to each his own.
This is always such a huge debate in here and actually every single bike forum I have gone in. Let me just say 1 thing(I'm sure someone will argue with me), Honda didn't exactly spend
that much time engineering this bike. Manufacturers are more concerned with price when it comes to their lower end vehicles, and most of the time they barely break even. They do this so that you enter their brand and hopefully are pleased and will move up models with your next purchase. Honda's bikes like the 600rr and 1000rr I am sure put A LOT of engineering time into balancing, road testing, wind tunnels etc etc. So I never go for the excuse 'if they thought (X) would make the bike better or faster they would have built it that way'. Not true. I know a Purchaser for Ford that specifically looks to find materials that save a penny on the dollar, that's part of his job to do, even if it means a different supplier from model year to next model year.
Anyways, I plan on going to 120/60/17, 150/60/17 when I need them. I have them picked out already and I calculated the rpm changes etc. by doing so. The only thing that really matters IMO is the rim size 4" inches. Now I have found websites that say their tires fit a 4" rim. Plenty of Ninjette owners have gone to 160's also and they have 4". There are a few people in here that have gone to 160's and they love it. Face it, I don't know of anyone in here that races their 300r yet? So street riding I don't see a big performance issue by going up 2 sizes other than you are just wasting probably an Inch or more of the tire (chickenstrip). But 'street cred.' matters to a lot of people also. As far as widths I've noticed different brand tires in the 160 size have different widths between their beads. The Diablo II I think is 4inches from bead to bead off the tire, Battlax was over 4", so that will determine how much the tire will arc also.
I couldn't give a crap what people think about the size of the tire, but I am brand loyal, and my brand only has 150/60 or 150/70
