Quote:
Originally Posted by Xist
This article is about $15,000 carbon-fiber rims for a Porsche 911, 19x8.5 and 19x12" rims, that are over ten pounds lighter than the stock wheels. One source estimated that would increase fuel efficiency by four percent:
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I don't see any possibility for 4 percent increase. They say that those wheels save 19 kg which is comparable to 35 kg of non-rotating mass. If car and driver have a total weight about 1500 kg, that 35 kg is just 2 percent compared to the total weight. In acceleration those wheels could give a gain of 2 percent. At a constant speed that same 19 kg difference doesn't have any effect. How the difference could be 4 percent?