just because SSR 18s may be lighter than OEM 16's doesn't neccesarily mean they reduce pwr or waste less hp. because the weight of the SSR is distributed across a larger radius, there is more rotational mass, ie heavier weight on the circumference of the wheel. so while the wheel may weigh less on the scale, the power it takes to rotate the wheel may be more than a 16in.iceNine said:RNN
Are you refering to wasting horsepower just because the wheel diameter (not the overall tire diameter) is larger or because most larger wheels are heavier? The SSR wheels (the Competition model anyway) in 18 inch are slightly lighter than stock US OEM 16 inch wheels.
Mass Moment of Inertia = I = | r^2 dm, wherebbrewer said:The issue of rotational mass always comes up when choosing larger rims. Can anyone define the equation that would allow optimizing weight vs mass when choosing larger wheels?
And when you complete the integral, you get I = mr^2.PlatinumWRX said:
Mass Moment of Inertia = I = | r^2 dm
LEAVE THIS FORUM AND GO TO A SMART! SCHOOL. ...And when you complete the integral, you get I = mr^2.
In short, when you increase the size of the wheel by 12% (16 to 18 inch), you increase the moment of inertia by more than 25%. So, if the 18 inchers are 25% lighter than stock, you won't notice the negative effect on your acceleration.
Here's a link that may be useful: www.dac.neu.edu/physics/a.cromer/Physics1192/Dynamics.html
Note: none of the above is a thumbs up or down for big wheels. The tradeoff of sidewall stiffness for increased rotational mass is up to the driver.
Your mileage will vary.