Bimmerfest - BMW Forums - View Single Post - All of these "doesn't handle well enough" comments need some perspective
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Old 01-04-2013, 06:31 PM
bmw_or_audi bmw_or_audi is offline
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Originally Posted by Jamesonsviggen View Post
The weight savings may be enough to counteract the sidewall attributes you brought up.
When it comes to larger wheels, the penalty is not simply the extra weight, but also the increased moment of inertia (AKA rotational inertia). Even with identical weight, the 19" will have higher moment of inertia than 18", which will affect acceleration. Moment of inertia for a small mass m scales with m * r^2, where r is the radius about the axis of rotation. Note how it is a squared term. The big heavy rim of the wheel will be one inch further out from the axle, increasing moment of inertia by about 11% (for the rim alone). I would have to make a back of the envelope calculation to know to what extent this affects acceleration, but in the hair splitting regime it may make a very real difference.
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