floyd

Ok,,i have added 5 lbs to my stock wheels by going to 18's from 17 factory on my gs430..how much slower did i just go? Anyone have a calculation of what it might be in HP to make up the diff or how much weight needed to be taken off the body?

Floyd

Yea,,yea...pictures of the wheels will be up soon..Antera 18' 309's chrome

Thanks guys..!!!!!!!!!

Vegassc400

I can't remember but 1 pound of wheel weight equals either 3 or 6 pounds of car weight. It's harder to move rotational mass.

redgs4

Calculations are good before you make a change, not so much after. Go to the track or get yourself a G-Tech or equivelent and measure. Anything else is just armchair quarterbacking.

SoCalSC4

The key is rotational inertia. You can't really compare a cast wheel and a forged wheel of the same weight- the weight will be concentrated differently throughout the wheels. The trick is to make the outermost portion of the wheel as light as possible, to reduce the polar moment of inertia.

Cast wheels generally need to be very thick in the rim bead area for strength- this increases the rotating mass. Forged one and three-piece wheels are require less material near the outer region of the wheel. Tis makes them appealing becuase it reduces the amount of rotating mass. Basically, the car will accellerate and brake more quickly, whereas a wheel with more weight will act more like a heavy flywheel.

The bottom line: even when cast wheels, the effect on performance is not easily quantified. If you have the data from several different wheels, you can run an analysis to get a better understanding of this, but at the end of the day, if you are performance-oriented, buy the lightest wheel you can afford.

tonytony

hey floyd, i sent you a pm.