[dradernh]

Originally Posted by POMFKIMOCHI

I think 45 would be safest, and I am obviously cognisant of the restrictions we face with the f22 platform.

I would be open to reducing 17s or making any other changes if required, but I'll need at least 235/255s with a Y speed rating at the very minimum as well (anything less isn't really an upgrade).

From Tire Rack's site, here are diameters for some 17" 45-aspect ratio tires:

235/45-17 25.4" Michelin PS4S
245/45-17 25.7" Michelin PS4S
255/45-17 26.0" Continental ECS.

The Continental is only a W-rated tire, but our cars don't go fast enough for it to matter. Or, if yours does, you'd probably have to run it at an event like the Silver State Classic Challenge before the W-vs.-Y speed rating would make a difference. My 2¢, of course.

The OEM rear tire is 24.7" in diameter, so you might have to adjust camber and/or roll the rear fender to fit a taller tire. Someone who has fit a taller tire in the rear may be able to tell you how tall a tire you can fit, and what had to be done to fit it (if anything). I've only gone up to a 25.0" diameter rear tire, and while a 5mm spacer, negative camber, and rolled fenders were part of the build back there, I don't know if the 0.3" difference in diameter required any of those modifications.