Z, I seriously thought about 225/45/17 with the OEM rims, but as simplespirit says, it's only 10mm. Not even a half inch wider. I doubt that size will bulge out on the stock rims. Tire Rack says 7 inch is OK for that size too. To add to the width change, a compound change like the Michelin Pilot or Goodrich KD will make a huge difference. I think with those tires, you've got a pretty powerful combination for the stock rim. I'm just thinking it would be great to stick 245's or 255's under the thing because the poor car weighs a lot for its size.
Simplespirit, to your point about 17 x 8's, since we have a McPherson front end, I am concerned about the rim hitting the strut tube. I don't like changing the offset to accomodate clearance issues because it changes the loading on the wheel bearing. A wider rim might clear on 18's and 19's but not on 17's. I am totally with you, I'd like 17 x 8 or 17 x 9 wheels to give me maximum flexibility for wider rubber.
I plan on all four corners being identical too, any text you read on setting up your car starts with, "it's best to have all four tires the same size." I also have a number of friends who spend a lot of time at track days with their Supras. I've heard them all say the ideal set up for a Supra is 315's all the way around. Assymetric sizes look cool, but I'm a function over form guy.
