16's vs. 17's

[silvachris1]

Originally posted by Jerriko:
Rotational mass only affects the drivetrain, not the front wheels on a RWD car.

Thank you. That answers my uncertainty. I said I wasn't sure if the rotational weight was for all for since it's extra that the car has to get rolling, or if it was only the drive wheels. I would have assumed it to be just the rear wheels/tires, but you know what they say about making assumptions. Anywho, .28 seconds is pretty well on with this math. My bests were .3-.5 seconds faster. But yeah, I'd say his question has been answered now, as well as mine.

[FunkZ]

Originally posted by Jerriko:
Rotational mass only affects the drivetrain, not the front wheels on a RWD car.

I'm 99% certain that it's ALL the wheels, not just the driven ones.

Tire Rack Wheel Tech:
Additionally, a vehicle's rotational weight includes all parts that spin including everything in the vehicle's driveline from the engine's crankshaft to its wheels and tires. This affects the energy required to change speed as the vehicle accelerates and brakes. As you would guess, reducing the weight of any of these rotating components will enhance the vehicle's performance because less energy will be required to increase or decrease their speed.

http://www.tirerack.com/wheels/tech/...jsp?techid=108

Also I neglected to mention that because larger-diameter wheels move more of the weight outwards, they increase the amount of force required to change accelleration. So yes, 17" wheels hurt performance somewhat over 16" wheels, even if the wheels and tires weigh exactly the same.

[dmw319]

hm thanks for all the responses guys!