So, to add back into the tyre debate...
I went and tested at a few tracks this weekend, and was determined to have some good runs with the Pit-shimizu 571/572 combo. Switched the settings on my car around to compensate (black front springs, harder roll damper oil, loosened the centre screw, adjusted ride-height to suit) and...... it was poop! no rear side bite at all, made it drive like the car was on ice, and had to be really careful about getting on power.
Went back to the R1's (which are now very very well used), adjusting the settings back to where I had it, and car was good again... going from a 25s lap to low 23's...
Biggest thing I think is that the R1's need a very weight forward balance to get them to work... whereas the Pit's need it on the rear. My 104 is setup with R1's in mind (plastic rear bracket, carbon axle, shorty pack far forward as poss), which really probably didn't help the Pit's to work well (but I wasn't going to re-wire the car!)
Still, an interesting test... will stick with the R1's for now, as they work well and last well too, so perfect for club racing IMO. It was an interesting test, and if I do get the time, I might well try setting the car up to test the Pit's again, but it's not a work of the moment thing...
Ed