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  1. #1
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    Question about tire size.....

    We were riding today, and my riding partner asked me why wheels are 700c, and not say 750 mm, or 710, or 690 and so on. Why was 700 chosen as the standard size. I know that they are the same diameter as tubular tires, and so you can easily swap wheels without changing the brakes, and etc... But, why was the size tubulars, or 700c, or for that matter 27 in. made the standard size?
    I have a guess, but I'd like to know if someone knows fer sher.
    Marko

  2. #2
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    The 700c is 622mm. Why is it the standard instead of something else .... Same reason all DVDs are the same format.

  3. #3
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    Because, just because. It's one of those mysteries of the universe.

  4. #4
    aka Phil Jungels Wanderer's Avatar
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    I'm just glad they finally settled on one.......

  5. #5
    Disraeli Gears Charles Wahl's Avatar
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    If you've ever delved into bike frame design a bit, you've probably realized how finely calibrated everything is, and how changing the size of wheels would throw all kinds of things out of whack in a hurry. My guess is that the Continental constructeurs and English ones arrived pretty much at the two very close wheel/rim sizes because it made frame design efficient and simpler, to accommodate the widest variety of sizes necessary with the fewest modifications to the frame configuration.

  6. #6
    Great State of Varmint Panthers007's Avatar
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    Just wait until some genius<koff> with a big and expensive marketing-firm, comes up with "Biopace" wheels. Then it begins... Do you want the 685/719C? Or the 692/707C? Or the.....
    How do you keep an idiot in suspense?

  7. #7
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    I think they sorted out the basics before the turn of the last century. Google "1884 safety bicycle".

    If they made the diameter larger, the frames would have to be wider so the spokes didn't get too steep, and smaller frames would cause the front wheel to hit your foot unless the frame were so long that you'd have to reverse your stem, which would make the bike handle funny.

    I probabaly can't even conceive of all the reasons, but many, many different combinations were tried and they hit upon "70cm" as the ideal size. I know Velocio felt a 50cm wheel with 5cm tires was the more ideal solution for many situations, though.

  8. #8
    Great State of Varmint Panthers007's Avatar
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    "700C" is not, nor has it anything to do with, 70cm - cm inferring centimeters. So none of it truly makes sense. I just had an utterly bewildered guy here to deal with a wheel-problem. I had to explain all this to him. I asked him if he was still confused. He said he was. I told him I was glad he was as only a certifiable lunatic could make sense out of this system. He agreed.
    How do you keep an idiot in suspense?

  9. #9
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    Except it isn't 70cm, it's 622mm. 700C is just the name of that particular size. There is also a 650 that isn't nearly as common.

  10. #10
    Great State of Varmint Panthers007's Avatar
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    And a 700A, too! Weeeeeeeeee!!

    "I'll be happy to see those nice, young men in their clean, white coats as they're coming to take me away!"
    How do you keep an idiot in suspense?

  11. #11
    Hair Club Member bernardmarx's Avatar
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    as I understand it

    I seem to recall that "700c," "650a" and "650b" are traditionally the French designations, derived not from the size of the rim, but the outside diameter of the rim plus the appropriate tire. We have always called "650a" "26x1 3/8" in the English-speaking world -- but now that the U.S. isn't really English-speaking anymore it's hard to even find a new bike that is mounted with 26x1 3/8 rims -- the new thing seems to be the 559mm "clunker" size (the so-called "26 inch" relic from the 40's) I thought we buried in the 50's. Apparently the mountain bike brought it back to life (I wouldn't know -- I still don't know why people push those clunkers around). The French "650b" seems to be a non-starter in the rest of the world, despite an effort to import this unneeded size, so close to the "middle-weight" 26x1 3/8 we have always used in the English-speaking world. (Of course, the whole Schwinn "S5" and "S6" middleweight sizes just muddies the water more.) Some see much uniformity and logic in bicycle tire sizes -- but how they do is a mystery to me.

  12. #12
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    A great article that will make it all clear as mud.

    http://www.sheldonbrown.com/tire-sizing.html

  13. #13
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    Quote Originally Posted by garage sale GT View Post
    I think they sorted out the basics before the turn of the last century. Google "1884 safety bicycle".

    If they made the diameter larger, the frames would have to be wider so the spokes didn't get too steep, and smaller frames would cause the front wheel to hit your foot unless the frame were so long that you'd have to reverse your stem, which would make the bike handle funny.

    I probabaly can't even conceive of all the reasons, but many, many different combinations were tried and they hit upon "70cm" as the ideal size. I know Velocio felt a 50cm wheel with 5cm tires was the more ideal solution for many situations, though.
    I'd never heard that before that sure makes a lot of sense. Also, wheels in the old days had to be large enough to handle unpaved or cobble stone roads so smaller wheels would not have worked well.

    And yes, I'm pretty sure the "700" designation indicates a 70cm outside diameter of the origial 700C size wheel/tire combination. It was the standard in the old days to make all of the wheel/tire combinations a standard outside diameter and to vary the rim size depending on the physical dimensions of the tires. IIRC the original 700C size was much wider than the typical tire today and had a larger outside diameter.
    1959 Bottecchia Professional (frame), 1966 Bottecchia Professional, 1971 Bottecchia Professional (frame),
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  14. #14
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    Quote Originally Posted by Ronsonic View Post
    Except it isn't 70cm, it's 622mm. 700C is just the name of that particular size. There is also a 650 that isn't nearly as common.
    Did you ever notice a 559mm mountain rim is actually about 22 inches? Yet everyone calls them 26.

  15. #15
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    Old English roadsters had/have 28" (635) wheels, with 90mm front axle spacing and 120mm rear hub spacing. They also have long wheelbases and relaxed frame angles (your feet won't hit the front wheel) AND they were made to handle cobble stones, dirt paths, gravel roads, etc. And they last FOREVER.

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