Junk in the Trunk:
 

Hey guys,

I didn't really know if this was on topic for this particular forum, but nothing else seemed to make hugely more sense. I'm looking into getting some 18" wheels with better performance tires when the next autocross season starts. My question then is whether or not I'll be able to fit 18"s in the back of the car. I know the car was advertised as fitting four wheels with tires in the back, but I'm guessing that referred to something comparable to the stock wheels / tires. Also, has anyone actually done that with the stock ones in the first place?

Thanks for any input.

Without tires mounted? Yeah. With tires mounted? Get the diameter. On an 18" diameter wheel, you'll run a shorter sidewall anyway...

I'd think you can fit them, just get creative and eat oatmeal that morning.

You should be sticking to the same overall diameter with tires mounted regardless of wheel size anyway, so I don't see why it wouldn't fit like the stocks. But if, for whatever reason, they're biger than stock, you can easily fit them if you're including trunk space. Two stacked on one side in the back, one leaning against the stack, and one in the trunk.

Lot's of people have put tons of different size tires inside their FR-S. SEARCH THE FORUM!

17s will be better for performance (lighter) and have a larger tire selection that is cheaper.

Exactly. For some reason the OP thinks 18" wheels will or should increase the overall diameter, which it won't or shouldn't anyway.

Key word highlighted. People do stupid things sometimes...

Sorry about not understanding much about replacing wheels. This is the first car I've even bothered to think about doing it on. The 18's I've been looking at would weigh about the same as the stocks and I was told I would get better performance because more rim means less wheel roll in corners. I wasn't exactly sure if the overall diameter was intended to stay the same in that case or not, which was the reason for my question. Thanks for the replies and advice on how to put them in the back.

^^ Bigger wheel puts the weight further out, so there's more rotational inertia even if the wheel is the same weight as stock.

If you're worried about sidewalls rolling get tires with stiffer sidewalls, not bigger wheels.

I put 225/40r18 in my trunk with seats down of course, so yes it can be done.