I was wondering if putting 245/35/19 in the back and 215/40/18's in the front would be ok? I like that rounded look plus I plan on getting some spacers. would they look funny because they wouldn't be as tall?

 

Brent, by putting a smaller tire on the Crossfire (front & back) I'm sure the over all aggressive "look" of the car will be greatly tamed,IMO. Handling shouldn't be adversely affected if you use a similar performance tire design at those smaller numbers.
Performance should actually improve thanks to the fact that your engine will have to spin less overall mass and weight. Also, with a "shorter tire in back, you will effectively be giving your car a lower gear ratio. Thus turning the 3.27:1 ratio into something more like a 3.50:1. Just by losing 1" in height on the rear wheels.
You didn't say your reasons for making the change, Performance, handling, or just to be different. But nothing changes the "feel" of a car more than installing a different set rubber on it.
Good luck.

 

by changing the diameter of the wheel, it will affect both your odometer and speedometer...

 

Well if I do get thinner ones, they will definitely be taller than the nearly bald michelins I have on there now. I looked at the specs and the 245's I want to get are only 2/10ths of an inch less in overall diameter.

 

Brent, after re-reading your original post, now I see that you were only thinking about going down one size. In that case, I don't think that you would notice much difference, if at all. Your cars appearance would probably have a different over all look, but unless you were parked next to another Crossfire (with stock tires) nobody would probably ever notice.
You mentioned that you liked the more rounded look of a "thinner" tire. Are you referring to the "cross section" view of the tire, in other words, what you would see if you were to cut a tire in half winding up with two "half moons".
In that case, you may want to look at getting a smaller diameter set of wheels (like the 17's off a Mercedes SLK). They use a taller aspect ratio sidewall to make up for the difference in height of our wheels. Since there is more side wall to deal with, they have a more "squat" or "bulged out" radial look about them when viewed from behind.

 

I am talking about the "euro" look, wide wheels with tires a bit smaller (width wise). Anyways dropping down a size gives MANY more choices on tires. i was looking at the new nitto INVO. It shows a 245/35/19 on their site but none of the online dealers stock that size.

 

Seems lika a fine idea to me. Only if you install the Eibach springs with them. I just posted my very minor tire rub photos so you can see that the thinner (lower profile) tire may work better.