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Old 12-16-2007, 12:24 PM   #8 (permalink)
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Camryaro - '92 Toyota Camry LE V6
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Based on what the almighty wikiality says, the second quote is incorrect since the distribution of weight on a car wheel isn't nearly as pronounced as on a bicycle, aka the ideal case of a mass at some distance from the center. Car wheels tend to be pretty beefy IME, and weigh more than or about the same as a tire, and since the disk or drum is rotating too, there's even more mass close to the center. This implies the moment of inertia is likely significantly less than .5mr^2 IMO. Offhand I would guess that a tire wheel combo has maybe ~25% more KE than a static body moving at the same speed.

This does bring up an interesting point though. If you've looked at tire specs, you may have noticed that wider tires weigh significantly more than their skinnier counterparts. Since all this weight is near the edge, I would guess that the choice of tire can influence acceleration/deceleration as much as or more than lighter wheels could.

That being said, the only fuel efficiency property that depends on mass in an ideal situation, Rolling resistance=mg(Crr), depends on mass alone AFAIK. While larger wheels/tires may hurt acceleration, braking, and handling, I don't see how they do anything to influence the energy needed to move a vehicle down the road.

Last edited by roflwaffle; 12-16-2007 at 12:26 PM..
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