I think standard tire size for the 00 R was 265/40ZR18. I assume that you can probably step it up to 295, but you're gonna have some wheel bulge. OE size is ideal for a good reason. For best handling the bottom of your tire contact pacth should not be wider than the wheel you mount it on.
Thanks for help, I have 275s now and was goin to switch over to nittos. So I was tryin to figure out what the biggest size that would fit on a 18x9.5 rim with no problems.
my y2k coobra 18x9.5's just came in the mail, i ordered vredestein sessantas sp? for them, 275 35 18 all the way around, when I get them mounted i will get some pics up for you