[JazzleSAURUS]

I think to answer your question, I'd have to reiterate this:
"So a comparable OD and width package in a 16" package will be lighter than an 18" package, but the 18" package will be a bit more communicative, and likely give up a bit of grip. That is, imo, why these cars come with 17" wheels. It balances ultimate grip, (compliance in the sidewall, which helps retain grip during transitions, as well as dampen road shocks from the tire to the wheel,) with communication, (a shorter sidewall is naturally stiffer, which communicates better and offers that 'razor sharp' feeling.)"

In going to an 18 it won't be bad, but you will notice some of the changes. If you want to minimize that, you could go with something like the 225/40. tire OD affects a lot, including gearing, (it's effectively your final, final drive...)

So you'll notice you will lose a bit of acceleration in going to a 225/40-18 based on gearing, and some based on the fact that you're likely adding weight to all 4 corners as well. Going with the 40 series sidewall will retain the majority of the sidewall that the stock 215/45 has, which will help with the negatives mentioned above in going to an 18" wheel.

One of the best ways to combat the gearing advantage you're losing is with a bit of extra power. Something like a JDL header and Delicious EcuTek tune will bring all that acceleration back, and then some, (with vengeance...) and should be perfectly reliable.

This is a bit part of why I've stuck with 17" wheels, aesthetically I think it works great, it keeps the weight down, and I get the benefit of taller sidewalls without the downsides of going too tall. If I wanted to go with an 18" wheel I'd get a taller package, and add power to combat the gearing disadvantage.