Is it worth a slower car? to me yes...i don't street race, and if I do take it to the track I'll throw the stock wheels back on. My car looks amazing, and I couldn't imagine myself w/ smaller 19" wheels. The 20's fill up the wheels wells perfectly.

My pics

 

Some of you need to do your homework before you make such general comments. Depending on the wheels and tires you get 20s could mess with your ride. I am not talking about it being slower or rubbing or anything like that I am talking about the extra stress that is put on the drivetrain from trying to spin heavier wheels and tires. It all depends on what you get but it can have a major impact on the performance and longesvity of your car. Also heavier wheels and tire will not only make your car slower but also make it stop slower.

G35 Coupe 6MT w/ PP & Aero
DG w/ Graphite Leather

 

I went to 19's from the stock 17's. Looks great. Remember that a 20 will only add 1/2" to the wheel well "fill" because after all, 20 is the diameter. Don't know about speed effect since I don't race, but the ride is at least as good if not better because of the Goodyear RS-A's being a relatively low end noisy tire. Cost is a factor. 19" Bridgestone SO3's are about $300 installed. My Zenetti 5 wheels were around $400 each. America's Tire gave me a $100 each trade-in for the stock wheels.

Wear and tear on suspension and drive train needs to be considered. On the SUV site, going to 22's vs 20's (from stock 16 or 17) generally requires a brake upgrade to overcome the additional stopping power needed. Also, ball joints will suffer early failure. As far as a G35, probably not nearly the concern because it's half the weight of a Tahoe type vehicle. Just my thoughts!

 

Well, this is my first post here, but since no one mentioned rotational inertia, I guess I'll post. Despite the fact that a particular 16" wheel may the exact same weight as a 20" wheel, the mass on the 20" wheel is spread out farther from the axel than a 16" wheel. A simple ring gets modeled as I = M*R^2 (Inertia = mass * radius squared). A complex shape like a rim will have a different formula, but the basic relationship is still there. A heavier wheel has more mass, thus increasing the inertia, but a larger radius will also increase the inertia quadratically. Thus the larger your rim, the larger "R" gets and the harder it will be to accelerate the wheel to speed. Once the wheel hits a constant speed (steady state) the rotational inertia won't really matter, but acceleration and deceleration performance will suffer with a rim with greater rotational inertia. This is getting long winded, so I'll stop but I hope at least a few of you get something useful out of this.

<P ID="edit"><FONT class="small"><EM>Edited by hayaku on 07/30/04 09:06 AM.</EM></FONT></P>

 

I was just going to say something about rotational inertia but you covered it. That's why I wonder how the performance of the 05's is going to be compared to the 03-04. 15 more HP but 1" bigger wheels, and we dont' know how much they weigh.

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Gonna order a 2005 DG 6MT Coupe soon!

 

But if the overall radius or diameter of the wheel plus tire doesn't change and the mass of the bigger rim is lower then stock... then there should not be any affect on accelleration. Basically if you have lighter 20's with the same overall diameter, I don't see how that will affect your performance.

 

As Hayaku explained in his post, a wheel + tire will have a more complex equation for the inertia calc. However, look at it this way. The weight of the tire is much less than the weight of the wheel. Therefore, it's diameter will have a much greater effect on rotational inertia. If the new wheel is actually lighter than the stock wheel, it may be a tradeoff, but keep in mind that the inertia is related to the SQUARE of the radius, while the weight is just a linear relationship.