Question about wheels.
 

So i'm currently looking for winter wheels on craigslist and wondering if ANY 17" wheels will do for my stock FRS. If one can only find 16" or 18" wheels what kind of modifications do you need to make?

Check sticky
http://www.ft86club.com/forums/showthread.php?t=7535

Don't worry I have been here (semi) long enough to check stickies before posting. Maybe I missed it somewhere in the wall of text, but the sticky doesn't seem to answer my question.

Read about tire and wheel fitment. Many things can "fit". 16-18 in general should be no problem. But there is no absolute answer. You have to factor width offset and tire size.

To answer your question as a yes/no., " any" 16-18 wheel will not fit. First make sure it has the right bolt pattern, 5x100. Second check the width and offset. In general wheels less aggressive than 8.5 +45 (or more aggressively 9 +42) will fit stock suspension.

Check that sticky for wheel specs people have confirmed.

Finally check tire size. Different size wheels tires should be fit to have overall diameter as close to stock diameter as possible.

If that's too much you can just check a site like tire rack and it will give you confirmed fitments and recommended tire size based on the wheels you pick.