I thought I would give my two cents on these tires since they're now being demoted to spare status.
Just for some background, my Z is a daily driver that will see the track occasionally (intermediate level driver). I bought these tires for extra grip without killing me when it decides to pour in the Houston area. I got them February of 2014 and I've done:
Sizes: 265/35R19...305/30/R19
- at least 20K miles
- 5 track days on the front
- 4 track days on the rear
Below is what's left on the rear:
As far as how these tire behave, they are very grippy in daily driving situations when new. Wet and dry conditions yielded stable and predictable handling characteristics. On the track, they were perfect for learning racing lines and the car's handling capabilities. These were very forgiving when you start to break loose; it's a gradual loss of the rear end. I tend recommend these tires to friends who want to learn how to track their Z. They have enough grip to fly around the corners, and the owners don't have to commit to buying a full set of wheels and tires for track use if they don't like the "track experience".
If anyone has any questions, I'd be happy to answer them. This is all I can think of at the moment.