Quote:
Originally Posted by Mark McM
Where did you see that? I've heard a different rule from Poertner, the 105% rule. That states that the rim width should be no less than 105% of the tire width for best aerodynamics. Poertner discusses the 105% rule here.
Based on this rule, the absolute tire width is not the predominant factor, matching the tire to the rim is. For example, a 23mm tire on a 24mm rim will actually be faster than 21mm tire on a 20mm rim. |
It's actually on the same article you linked
Quote:
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In strict aerodynamic terms, this added width comes at a cost of roughly 1watt per 2mm of tire at low yaw angles. However, the big penalty can come at moderate yaw angles as the tires approach the width of the rim.
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I think of it like if you have a 17mm rim and the tire's already far beyond 95% of the rim width, what happens if you increase the tire by 2mm.