bigger wheels in back then front?

Ive noticed that a lot of new sports cars/sportier cars come with bigger wheels in the back then the front ie a ferrari spider i saw and a nissan 350 Z (the z has 19's in the back and 18's up front). If buying new wheels would i have an advantage getting like 18's out back and 17's out front or would 18's all around be better.

Actually, 17's all around would be better. Since we have a heavy live axle instead of independent rear suspension, you NEED some sidewall compliance to get good grip.

The Ferrari is a totally different car, but most cars running gigantic rims are actually sacrificing both ride AND handling for the Fast and Furious "bling bling" look. More isn't always better.

In fact, 17 front / 16 rear (same width) would probably be an even better combo, but it looks a little funky and more importantly prevents rotating the tires.

hmm i can definitly understand that thought from a stand still to full throttle but would that compliance not hurt you a bit in an autocross/road race forum? My next question is has anyone used 17's all around and then switched to 18's? What was the difference like? Did it hurt your times at all, did it help, or was it negligable

My opinion :D

17's would generally be lighter unless you spend the big bucks. Less unsprung weight is what you want. I agree with the compliance issue to a certain extent. By going to a lower sidewall tire, you do reduce the compliance somewhat. It acts like your adding a stiffer spring. How much just depends. Look at the CP cars and they run 16" rims (of course, they have to anyway!!).