iROK24/7

OK I'll chime in as an engineer. You're concerned with weight, but weight DISTRIBUTION is the more important issue here. The reason drag racers use small diameter (15") wheels is because the more weight you have near the outer diameter of a wheel, the more force it takes to rotate it. So what's heavier - rubber or metal? Our wheels have an overall outside diameter of 26" - bigger wheels use low-profile tires to arrive at the same 26" diameter as a smaller wheel with high-profile tires. If you load up the edges of your 26" diameter with METAL (rim), it makes it more difficult for your engine to rotate the wheel. By keeping as much of the heavy metal near the center of the wheel and letting the edges be composed of rubber & air, you achieve more rapid acceleration.

Now that you know how acceleration is affected - it's time to think about cornering performance. The larger rim will add rigidity to the wheel (metal is stiffer than rubber) and improve cornering - hence nobody uses 15" rims in Autocross (to my knowledge). Since you want to have a car that performs reasonably well in BOTH categories, IMO you need to compromise and have a wheel size of perhaps 18". You definitely don't want to choose a wheel at EITHER extreme of available diameters.

howarmat

27.2" diameter boss

iROK24/7

Thanks Matt!

Point being that the wheels have a fixed diameter... made up of rim + tire. Question being how much of that diameter do you want to be rim?

Riptide

http://www.w8ji.com/rotating_mass_acceleration.htm

That's true that in general metal weighs more than rubber. But IME the tires weigh more than the metal wheels. The stock pirelli 235/55/17 weighs close to 28 pounds. The stock 17" wheel weighs significantly less than that tire.

iROK24/7

Sorry Riptide - to be more specific, we're talking about the difference between two thin bands of side wall rubber versus the outer couple inches of rim...

m0nkeydump

I think 20's look better with the car lowered. For some odd reason, 19's look fine to me on stock height.

m0nkeydump

Also, I just wanted to add that unless you plan on tracking frequently and are extremely worried about your fastest 0-60 time, the difference would cause negligible decrease in performance as far as regular driving. The engineer ^ there made good points.