Going with 18" wheels won't change the overall tire diameter, and therefore shouldn't have any more wheel well gap than it would with the 20" wheel. Having seen the car (with 20's) in person, I can tell you that there's not much gap.

 

From the factory, all Camaros will have the same overall tire diameter, right? So I assume that means they'll all fill the wheelwells the same amount - it's just a matter of how much is wheel and how much is sidewall.

 

Right, you would take numbers from one and add to the other.

 

I like the 18". Why such big wheels, aftermarket 20"s especially are sooo heavy, kills MPG and acceleration.

 

That's pretty much exactly what I said.

 

I totally agree on that assessment. You need to fill the gaping hole somehow. You either end up with a 50 series truck tire, or a freaking blinged out g-ride on 22's. Argh.

 

That's what I thought you were saying, but I did not find your wording clear so I was trying to verify that what I was inferring what what you were implying. Note the "?"