I posted this on my local philly dsm board then decided to share with you guys too.

Rim sizes do affect your power. If you have two sets of rims that are the same length, width, and weight, it does not mean that they will work the same. It has everything to do with the distribution of the weight.

A 14 inch rim will outperform a 17 inch rim anyday even if they had the same diameter, weight, and circumference after tires were put on because of how the weight is placed. Because the heavy metal in the 14 inch rim is more centered, rotational inertia (RI = sigma x m x r^2) is significantly less then the 17 inch rim which has it's mass spread out farther out on the diameter of the tire.

Based on that notion, a lighter 17 inch rim may still lose to a heavier 14 inch rim, just based on the placement of the weight.

This same process goes for brake rotors and underdrive pulleys too. Since UDP's are lighter and smaller, they most likely do what they are suppose to do. On the contrary, big brake rotors will hurt your power, but it makes up for it in other ways... like... not..dying.

For example, I was watching Speed channel last night, and they had an RSX on the dyno before and after big brakes... they actually lost 5% horsepower from their big brakes.. it was like 8-10 horsepower. All from a one inch or so increase in braking diameter.

Back to the tires. So now knowing that mass placement on the diameter makes a difference, how would a thin-spoked rim perform versus a thick-spoked rim of the same mass and diameter? The question here is that with the thin-spoked rim, the bulk of the mass is at the outer most part of the rim and the center, while the thick spoked rim would have a more equal weight distribution... I don't know know the answer myself because I'm not geeky enough to run those numbers in my head, but wouldn't it be interesting to know that a thin spoked lightweight rim is actually worse then a bulkier thick spoked one just because of how the weight is placed?

Ah, the misconceptions of life.

16.1 @ 87.11
http://www.virtuallyinfamous.com

ARD 57mm tb and p&p manifold, Neuspeed STB, Pro-kits, Illuminas, Injen CAI with K&N, 2.5" pacesetter catback,
AF/X UDP, Rear STB, Powerslot rotors, RRE SS Brakelines.