Yeah much cheaper to practice and correct form than buy new tires suspension or a new motorcycle

 

Thanks guys - It's not the size of the rear that I want a 165 for, but more the fact that I want a racing slick and I'm just not seeing them in a 140. On my R1 I notice a BIG step up when going to a slick, even from a competent track tire like a Dunlop Q3.

The Diablo's are great street tires, I just don't know how they'll hold up on a track when things get cooking...

 

You can get slicks in those sizes, isn't a 130 or 140 what they run for the 250 class

 

The slicks I'm seeing for 250cc are all at least 150/60, (125's run 115/70s!).

I ended up running a BT003 rear (with a Bridgestone R10 take -off front) in my first race and it did the trick so far. Bridgestone's contingency payouts dwarf Pirelli's, otherwise I'd just run the Diablo II