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Old 03-31-05, 05:58 PM
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Originally Posted by LordOpie
Isn't the diameter of the wheel a factor? If so, then a road bike would be 27/26 times (4%) more efficient (plus whatever other factors), right?
The importance of wheel diameter is way over-rated. The reason road wheels are 700c is that's the size that road wheels come in. Tire selection and wheel construction is much more important than wheel size, and it's much easier to find wheels and tires built for speed in the 700cm size. I've recently read about two trends. First, MTB manufacturers are now pushing "29ers" with so-called 29" tires that use 700cm rims. Second, road bike manufacturers are now pushing bikes with 650cm rims -- 26" for those of you on imperial units. It seems each side is convinced the other side is right!

It would be a good thing for the industry to move away from rigid standards. It's silly not to have wheel size scale with frame size. Short riders in particular suffer -- it's hard (some would say impossible) to make a bike with acceptable geometry and 700cm wheels for someone under 5'4". Smaller wheels might help you get a better fitting bike if you are smaller than average.

Ken Kifer has a great riff on the subject:
"One of the oddest tales, and also clear proof of how us cyclists let ourselves be pushed around, is the story of tire sizes. When I started riding as an adult, all the bikes had 26-inch tires. My first "10-speed" (6 useful gears) came with 27-inch tires, forcing me to buy tires at bike shops (which are hard to find on a tour). A dozen years ago came a "great" improvement created by shifting from 27-inch to 700 cc tires. Article after article raved about the improvement. The only difference I can see is the need to stop at a bike shop rather than Kmart. Then came a new shift, where to? -- the 26 inch bike; only the tires on this bike are a different size from the old 26 incher. Can't you tell you're being flimflammed? Slight differences in the diameter of the wheel have no noticeable effect. The whole purpose of the different tire sizes is to force you to buy tires from one company rather than another or at a bike shop rather than a discount store."
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