I ended up going w/ 235/40/18 on my last Z... didn't rub at all. I had the 245's trial fitted and got a bit of rub on the front at a full turn.. It depends alot on the particular car and how much "sag" it has in the suspension, and some other things im not extremely positive about.. The best bet is to put them on and see... give the wheel a full range of motion, and remember that if your turning while going at speed, the suspension will give a bit and may rub. good luck!
:i am getting 245/40/18 all around my n/a z, will i have a prob with rubbing anywhere on the car when i turn or otherwise?(the guy said it was the righ size for the car?!)