If you have more than a few thousand miles on soft compound tires there can be enough wear on the old tire to make it significantly smaller than a new tire. On an econobox it won't make a lot of difference; on a sports car you can feel it.

If you are happy with the way your Z has been handling, there's not much sense in spending the extra bucks for better-than-OEM tires.

I replaced the RE050 with 760's on my S2000 before and there is definitely a difference. If you are just DD'ing the car and not really planning on auto-crossing or driving fairly aggressively(canyon carving) and more worried about tire wear the 760 is a decent tire; but from my experience the 760s feel greasy when you get near the grip limit on the tires and are not as predictable and forgiving as the RE050.

i'd say the RE050 Pole Positions were pretty good. Not as good as the S04's.

The factory RE050A's.. okay tires.

you want the RE11's. those are real nice. :D

RE-11's are so yesterday. The new RE-71R's are the tires to have if you're going to drive the car hard.

Michelin Pilot Super Sports consistently come out at the top of tire comparisons. I run them -- they are quite good.

Bridgestone RE050s
 

After a repair, Bridgestone does not stand behind them as " high performance" , according to Tire Rack's website. I replaced mine. $370. Bummer.

Interesting the RE-71R's have a better wear rating than the RE050s.

had the re050s and swapped to potenza s04 pp which i feel grip harder. Of course the older tires were getting pretty worn, not exactly at the wear indicated yet though. I don't shop firestone normally, but since they are owned by bridgestone i stopped in and got a better deal then my online searches pulled. The dealer wanted big money.