Kurosaki,
The tires are awesome. I have 3 track days on them and they are holding up really good and the wear has been minimal on the ninjette. Which is exactly what I was told by the Bridgestone distributor. (
www.stickboyracing.com)
Being that these tires are actually made for bikes bigger and heavier than the 250, they provide excellent grip on the little Ninja. They warm up pretty quick too.
Granted, I'm not a FAST guy by any means and am a new rider. As I have been slowly progressing and getting a little faster (glad I did the Ed Bargy race school) I still have not felt any sliding or unexpected movement. I think one would have to do something pretty drastic to get the bike out of shape with these tires.
One thing that I did notice is, although the rear tire is slightly wider than the stock tire, I noticed that the bike turned sharper than with the stock tires. These are radial vs the stock ply's and the profile is different.
That was my observation and would be interested in listening to your feedback too.
I think you'll be very pleased with these tires, in my opinion, they are worth every penny.
-Joel