[SpencerC_6MT]

Even if you're not interesting in Apex wheels, they have a fantastic fitment guide for the F2x to help you decide on a setup. For a brief overview on your options though:

If you want to keep a square setup, the absolute maximum you can manage is 255-section. That requires very aggressive camber and perfect size/offset wheels, so I wouldn't suggest that route. 245/35/18 square is pretty manageable, but will also require camber plates. I'm running 245/40/18 since I prefer extra sidewall, but fitment is tight. 235/40/18 seems to be the happy medium for our platform, and 18x8.5+40 is the fitment to go with it.

For staggered, you'll probably want to stick to 235's on the front, and 255's or 265's on the rear. It seems to me like most staggered folks run an 18x9.5r and 18x8.5f, but I never did a deep dive on it. 245f/265r is probably the maximum grip setup you can run on the street, but will also require camber plates up front.

I wouldn't suggest changing from 18" personally, but there are options. 17" wheels with a lot of clearance will clear stock brakes, but you're cutting it real close, especially on the rear. 19" is totally possible, though you'd lose some ride quality to the sidewalls.