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Wheel help(4 posts)

Wheel helpBikeViking
Mar 28, 2002 1:05 PM
I am writing a computer program that calculates bicycle gearing for my C++ class and I have a question or two.

Is a 700C wheel actually 27"? Are they one in the same? If not, what is the precise measurement of a 700C?

Is a 650C wheel a 26" wheel? If not, what is the precise measurement?

Are there generally accepted wheel diameters (w/tires) for each of the above wheel sizes?

I hope this doesn't sound TOO dopey!


re: Wheel helpTJeanloz
Mar 28, 2002 1:28 PM
700c wheels are not 27" wheels. Somebody probably knows the exact size. I can't remember it right now.
650c wheels are not 26" wheels.

There are no standard diameters- because different tires have different profiles. BUT if you look at a computer set-up chart, it will give a good idea.

You can, of course, quite easily do a "roll out" test to determine the exact diameter of your wheel/tire.
re: Wheel helpmja
Mar 28, 2002 1:29 PM
No, 700C and 27 in. wheels are not the same size, the latter is larger. Besides, circumference is probably what is required in your calculations and that depends as well on the tires. (I use 2095 mm for road and 2042 mm for ATB.)

These are not dumb questions! I used to think that the "C" was cm or mm or something. It isn't. Sheldon Brown's website has good info on tire specs.
700x23 = 26.25 inch diameter (approx) (nm)Kerry Irons
Mar 28, 2002 7:46 PM