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  1. #1
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    So...a 26" rim is not actually 26" in diameter..?

    Just measured one the other day and was a bit suprised when it didn't turn out 26".

    How come they claim the rim sizes more then they are? Or is it because a 26" tyre fits on the rim...but the rim isn't nessesarly 26"?

    thanks!


  2. #2
    Senior Member foulmouthfool's Avatar
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    the inflated tire on the rim measures 26"

  3. #3
    Mad bike riding scientist cyccommute's Avatar
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    Quote Originally Posted by foulmouthfool
    the inflated tire on the rim measures 26"
    It's even worse. It kind of like the earth's sea level. The 26" tire is of a specific size. Most tires aren't 26" in diameter either. Slicks are probably smaller and, depending on the knob size, knobbies are bigger.

    It gets even worse. A '26"' wheel for a mountain bike has a rim diameter of 559mm. That's for tires that are decimally sized like 2.125" or 1.95". But there are 26" wheels out there that take 2 1/8" tires which are sized differently from decimal tires. A 650C rim (26" tire using 2 1/8" tires) has a 571mm rim diameter. A 650B (still a 26" tire) has a 584mm rim diameter. Thankfully you don't run across the latter too often. If you happen to have 24" wheels or 20" wheels (kids bikes, recumbents) you do have to be aware of the issue, however.
    Stuart Black
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  4. #4
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    Read this, and all will be revealed.

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

  5. #5
    Bikeless Member cream.soda's Avatar
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    yeah, tire sizes are pretty messed, my high rollers on my fusion say it's a 2.1 inch tire on it, but in actuality it's closer to 1.95, a la mountain bike action's big tire comparo. my rockhopper's got 2.00 inch adrenalines on it and when stuck next to the high rollers, they're a full inch and maybe even an extra half taller than my fusion's wheel.

    there's no standard for measuring tire sizes so right now it's all over the place. according to just the numbers, my high rollers are bigger than my adrenalines, although the adrenalines are at least an inch taller and a quarter inch wider... (=.=")

  6. #6
    Banned. Jason222's Avatar
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    Now I'm really confused. 559 mm is 22.3 inches, not 26? Did I do the math wrong?

  7. #7
    Mad bike riding scientist cyccommute's Avatar
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    Quote Originally Posted by Jason222
    Now I'm really confused. 559 mm is 22.3 inches, not 26? Did I do the math wrong?
    Yea you did your math wrong. It 22.0"

    So you can see that even that mythic 26" diameter with a tire mounted is way off, unless you ride tires that are 2" tall from bead to top.
    Stuart Black
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  8. #8
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    Hmm, thanks guys.

  9. #9
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    It's even worse !!!! A 29er rim isn't 29 inches either.

    Yes tire sizes are messed up. But you have to realize that this is marketing, not engineering. If we got more specific, it would probably just confuse customers more than they already are.

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