Originally posted by 510dat
Ok, only dealing with tires...
You want different tire sizes based on what you are trying to accomplish. If you look at a 'funny-car' drag racer, they have giant tires in the back, and bicycle tires on the front. Since they don't really have to turn, lighter fronts are better. But, since you and I want to be able to make that U-turn, you need bigger tires on the front (well, wider than those bike tires).
It's all about ratios. The wider the fronts are compared to the rears, the easier it is to turn. But... you don't want it to get twitchy, because curbs are not your friend.
The wider your rears, the more likely you are to go in a straight line, and the more acceleration traction you have, but the harder it is to turn.
If you have lots of power, you need big rears to get it to the ground. Small tires will spin (more) easily. If they spin while you are taking a fast turn, your rear completely loses traction and your car spins around, too.
So, wider = more grip on that end (except in rain, when wider may/can = hydroplane, ie surfboard).
Stock, the 350Z is a bit wider at the rear (225 front, 245 rear). This will mean better traction in the rear, so you will have good straight line traction, but tend to 'plow' in a turn. Not badly, just a bit. This is generally safer than the opposite (old Porsche 911's can get real twitchy because of all the weight in the back. Notice the newer models have very wide rears?); most production cars have this tendency built in.
Lots of people like putting bigger tires and/or wheels on their car. Wheels bigger than 17in are mostly for show, and they get much more expensive. The advantage to bigger wheels is a bigger contact patch front to back (think wagon wheels), and slower wheel speeds at faster car speeds.
The downside is, the bigger the wheel, the heavier it gets. And even worse, the farther away from the hub that weight is. Physics says, the farther from the hub your weight gets, the harder it is to spin it. So a 20 pound 14" wheel is going to be easier to spin than a 20 pound 17" wheel. And, the more energy you spend spinning your tires, the less energy you have to accelerate your car.
So what do you want? If you want to drag race, get big rears. If you want to autocross, probably getting the same size (245-ish) all around is better. If you just want to look good, get 20" chromed wheels. But if you get spinners we will have to hurt you.