Performance definition on wheels, size, etc...

[kcederwall08]

This all seems fairly correct to me so far..

There is a slight performance gain with switching to a larger wheel diameter with a lower sidewall tire. I have absolutely noticed the difference myself when i put on my 18's. Quality tire selection is pretty good for 17's too, however it seems there are even more performance tires available for 18's.

One thing you have to keep in mind however is that when you decrease your sidewall height you are making the car more responsive, giving it better transient grip.  The steady state grip will not improve however, so this change in sidewall will only really help your car have better grip while transitioning. There is such thing as to small of sidewall also. As said before the optimum sidewall would be extremely small, but the car would be nearly impossible to drive for any person.

Someone also mentioned wheel width too, which is another very important factor for increasing cornering grip. More tire width will actually increase your steady state grip during corners (and transient grip also i believe) as apposed to a smaller sidewall only helping drive-ability and transient grip. You can also get too wide of tires, but that would be fairly difficult for a heavy car like a charger on street compound tires. If you talking race tires, you could have too wide of a tire that wouldn't heat up properly and get into its optimum temp range, but thats a whole other subject.

But i think the performance and drive-ability gains of switching to a larger and wider wheel are more than worth it. The ride may be a little more bumpy with a smaller sidewall, but if you care about performance you shouldnt really mind it all that much. People often try to point out that 18's or 17's are super heavy, but with a good quality wheel they should be relatively light for their size. Also another important factor is you can get much larger brakes underneath larger wheels, so theres another reason to upgrade 

[dangina]

So put 16" on the front and 17" on the rear.  Can't go wrong with the looks of that. 

looks nice but not that great for the handling - go 17's all around but no bigger than 18"

[Musicman]

Just buy better tires   

[HPP]

Just buy better tires 

True, but most guys aren't willing to plunk down $500 per tire for ZR rated 15" handling rubber.