With the powers I have had the rear tire slide a bit when turning.. maybe there has been a bit of debris or something else.
There's a bunch of reasons for that, I wouldn't be super quick to ditch the tires you have - unless they are already in need of replacement.
What was the temp like? Wet? Dry? Air pressure in the tire? See any dark sports on the road (oil/diesel)? Were you a little heavier on the throttle that day? There's a ton of reasons why the tire might have slipped. Sure the one it was, could have been the tire. But plenty of people really like those tires and have reported great grip.
It's pretty amazing how much you tire being 'off' will affect things. I went for a ride on a loaner S4R one day and she just didn't want to turn in. Check the tires pressure, front was fine, but rear was lower than I usually ride. Added a few PSI and she went from lolling into the bends to be light and lively - a marked difference.
I guess I'm jsut trying to say, eliminate possible other cheap or free culprits before you drop your hard earned dough on different tires that might not make a difference if something else is at fault.
