Brad,
I run 215/45/17's and 285/30/18's with 32psi front and 38-40psi rear with good results. I should mention that I have racing swaybars and eibach springs with bilstein shocks. Good balanced feel with crisp turn in and very predictable handling through the turns. I've noticed that, for street driving, lower pressures make the car feel spongy in the turns and less stable. Hope this helps.