Think again.
I just put some Yokohama Advan AD08 tires on my BRZ and I went with a 235/40-17 size.
Here are some comparison pics:
This is the new tire on an 8" wheel compared to the old one on the stock rims.
Looks bigger, but you would expect that. One's an OEM touring tire, the other is an aftermarket Extreme Performance tire made for AutoX.
But look at this comparison:
Again, new tire on 8" wheel on the right. The left tire is also on an 8" wheel, but it's a
245/40-18 Continental ExtremeContact DW (which Tire Rack doesn't seem to carry any more.
) I knew something was up when I noticed my new tires had more pinch than the 245s I had for my Legacy.
The 235 AD08 is listed as a 9.5" sec width, and the 245 ECDW as a 9.8" sec width at Tire Rack, but they're nearly identical in width when mounted to the same width wheel. So if you're going to be pushing the limits of what will fit, always double-check the tire width. If you go with a really high performance tire, be aware that the tire manufacturer might have fudged some numbers to get as much width as possible for the size.