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  1. #1
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    How do you size tires and rims? and other bonehead questions?

    I am anxiously reading all the threads I can in order to learn more about bicycles and biking. I keep running into terminology about that I don't understand like 36h 40h? What other terms do you use to describe hub size, rim size, wheel size, et? and what does freewheel mean?

    I tried searching on these terms and keep coming up with posts that use these with no description or, with google, articles that use these with no description.

  2. #2
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    The terms 36H, 40H, etc. refer to the number of holes in both the hub flanges and the rim and, obviously, to the number of spokes needed to assemble the wheel.

    Hubs are either front or rear. With few exceptions, front hubs are 100 mm wide measured over the outer faces of the locknuts referred to as the OLD (Over Locknut Dimension).

    Rear hubs vary in OLD depending on the age and how many rear cogs they were designed to use. Old 5-speed" hubs were 120 mm OLD. Newer 6 and 7-speed hubs are 126 mm and current road 8,9 and 10-speed hubs are 130 mm OLD. Mountain bikes have used 135 mm OLD rear hubs for years.

    Rims are described by the diameter to the tire bead seat using the ETRTO (now ISO) convention. Rim terminology is so involved and so confusing that entire articles have been written about them. Current common sizes are 700c (ISO 622) for road bikes and 26" (ISO 559) for mountain bikes. Older 27" rims are ISO 630. Sheldon Brown's web site has a very good explanation of rim sizes.

    Tires are described by their rim diameter and width in either mm or inches. Tire sizing is even more obtuse than rims. Again, see Sheldon Brown's site for good descriptions.

    A freewheel is the one-way ratchet that locks up when you pedal but "freewheels" when you stop pedaling and allows you to coast with out the cranks turning. The term "Freewheel" means both the ratcheting body and the collection of cogs that provide a choice of gears. A freewheel typically threads onto the rear hub as a complete assembly. Newer rear hubs use "freehub bodies" where the ratcheting body is built into the hub and the cogs are slipped on as a group called a cassette.

  3. #3
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    Woah! Smart!!!

    Thanks

  4. #4
    Jonnys ilegitimate Father cavernmech's Avatar
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    Quote Originally Posted by HillRider View Post
    The terms 36H, 40H, etc. refer to the number of holes in both the hub flanges and the rim and, obviously, to the number of spokes needed to assemble the wheel.

    Hubs are either front or rear. With few exceptions, front hubs are 100 mm wide measured over the outer faces of the locknuts referred to as the OLD (Over Locknut Dimension).

    Rear hubs vary in OLD depending on the age and how many rear cogs they were designed to use. Old 5-speed" hubs were 120 mm OLD. Newer 6 and 7-speed hubs are 126 mm and current road 8,9 and 10-speed hubs are 130 mm OLD. Mountain bikes have used 135 mm OLD rear hubs for years.

    Rims are described by the diameter to the tire bead seat using the ETRTO (now ISO) convention. Rim terminology is so involved and so confusing that entire articles have been written about them. Current common sizes are 700c (ISO 622) for road bikes and 26" (ISO 559) for mountain bikes. Older 27" rims are ISO 630. Sheldon Brown's web site has a very good explanation of rim sizes.

    Tires are described by their rim diameter and width in either mm or inches. Tire sizing is even more obtuse than rims. Again, see Sheldon Brown's site for good descriptions.

    A freewheel is the one-way ratchet that locks up when you pedal but "freewheels" when you stop pedaling and allows you to coast with out the cranks turning. The term "Freewheel" means both the ratcheting body and the collection of cogs that provide a choice of gears. A freewheel typically threads onto the rear hub as a complete assembly. Newer rear hubs use "freehub bodies" where the ratcheting body is built into the hub and the cogs are slipped on as a group called a cassette.
    Wow....a smart, detailed response without any smarmy sarcasm or derision at asking a question without doing a search. What has Bikeforums come to.
    The key to happiness is not in having more, but in developing the capacity to enjoy less.

  5. #5
    Senior Member Bill Kapaun's Avatar
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    Go to the sticky at the top of the page-

    sheldonbrown.com shortcuts

    Many of the links are fairly self explanatory.

  6. #6
    Senior Member Retro Grouch's Avatar
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    Quote Originally Posted by cavernmech View Post
    Wow....a smart, detailed response without any smarmy sarcasm or derision at asking a question without doing a search. What has Bikeforums come to.
    Yup. Hillrider's GOOD!

  7. #7
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    Quote Originally Posted by Retro Grouch View Post
    Yup. Hillrider's GOOD!
    Yep. I'm taking back all of those mean thoughts about him.

  8. #8
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    Quote Originally Posted by Retro Grouch View Post
    Yup. Hillrider's GOOD!
    Thank you. That's high praise indeed.

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