DO 20's slow your car down?
 

Im getting rid of my aftermarket 20in wheels for some factory 18's.
Will I see a dramatic increase in performance due to some weight loss??

Ive had the 20's since day one.
Never driven a G with factory wheel.

Sorry if this is a dumb question

not a dramatic increase...

http://i51.tinypic.com/2j4ripg.jpg
http://i56.tinypic.com/t9xem8.jpg

Yes it does. Rotaional Inertia. Take a weight, tie it to a string and try to spin it around in the air. The heavier the weight, the harder it is to spin.

It's proven to bring down WHP. If you care about HP, then I would use lightweight wheels. If you can barely drive over speed bumps or pebbles on the road, it shouldn't matter.

anyone know how much weight im shedding?

It all depends on the wheel, but if you're riding around on a cheap set of 20's, odds are they're heavy. You may lose upwards of 10lbs per wheel, and YES, it should make a noticable difference in acceleration and braking capability.

If it's the weight on the outside of the diameter you are worried about, then we should be discussing TIRE weight, not wheel weight

^
Yes however a larger diameter wheel has most of its mass towards the outside diameter of the tire. So they go hand and hand.

Most whee/tire packages have their mass toward the outside. Whether it's the wheel or tire.

Yes they do, but they cause other issues too like more stopping distance and extreme wear on the entire suspension....:OHBOY:
Gary

Why would they if the tire/wheel package is lighter than what it's replacing?

Not that difficult for let's say a forged 20" Volk on Michelin sport pilots vs OEM G37 19s on Bridgestone RE050 run flats.

Thank you for getting rid of those rims.

Yes it does, i had 20s before ( heavy wheels) i felt like i was driving a Civic.

IMO whether you get the performance increase or not you need to take those rims off ASAP

with those pics you have posted up there, you will notice a drastic change! hahaha...