I decided to stick with 285-35-19 in the rears and 245-40-19 fronts on my Nismo wheels. As going with the 265/305 setup would lower the car more and throw off the speedo. And I didn't want to do that, I am too low as it is now scraping everywhere.

How do you like the 285's? Did you notice significantly improved straightline traction over 275's?

springs + 265 fronts and 285 rears. sounds good to me. maybe I'll space them to flush the tires.

I like them alot, did not notice a big improvement but then again I only had my Z for a short few months before I got those wheels/tires. I think 285-35-19 is perfect for the Z. On Sport or Nismo wheels.