View Single Post
      03-15-2009, 05:15 PM   #35
urbo73
Captain
United_States
57
Rep
754
Posts

Drives: 2021 BMW M340i xDrive
Join Date: May 2006
Location: USA

iTrader: (0)

Quote:
Originally Posted by swamp2 View Post
An interesting part of this is the numerous results we've heard about the 18s ever so slightly outperforming the 19s. Seems if we believe such tests it is the moment of intertia effect, not the weight.
Exactly! The weight difference being negligible, moment of inertia is what counts. And though I don't know the precise weight *distribution* of the 19" OEM wheel (and thus can't say what 19" wheels would need to weigh to perform the same as the OEM 18"s - the difference would have to be pretty large), I do know that it will have most of its weight (mass) towards the outside of the hub. So it will have a higher moment of inertia and thus be more resistant to acceleration since I=mr^2

This is why smaller wheels are better in racing/track/etc. Only go as big as you need to clear the brakes, etc. Or go big for looks.
Appreciate 0