metric and standard wheels
11-23-04, 09:54 PM
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metric and standard wheels
I told a bike store guy I needed a 27" wheel and took home the one he sold me, but at home I realized that it's a 688mm, not 27". It seems a little off, but technically it should only be off by a 1/10 inch at most. Is that a big difference? Will it still work? Should I even try or should I take the wheel back?
11-23-04, 10:24 PM
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Dude, I think you're in the clear. By my calculatornations, a 27" wheel is 285.8 mm, which is 2.2 mm smaller than your wheel. 1/10" equals 2.54 mm, so you're within tolerances. The wheel will probably shrink a little once you put some weight on it and ride it, which was probably factored into design. shrinkage may be worse in cold weather, however...
Last edited by dafydd; 11-23-04 at 10:32 PM.
11-24-04, 07:24 AM
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I've never seen a tire marked 688mm! The traditional tire sizing was based on the outside diameter. However, this is only a nominal measurement and you will find tires that are oversize and undersize. The important thing to know if a tire and rim are compatible is the bead seat diameter. As a result, all modern tires and rims have two sizes marked on them, the traditional size based on nominal outside diameter and the ETRTO/ISO size based on bead seat diameter. For a 27" tire, the bead seat diameter is 630mm. If there is an xx-630 marking on the tire, then it will fit. BTW, the xx is the tire width, in millimetres.
Refer to https://www.sheldonbrown.com/tire_sizing.html for a good explanation of tire sizing standards.
Refer to https://www.sheldonbrown.com/tire_sizing.html for a good explanation of tire sizing standards.
11-24-04, 12:12 PM
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Originally Posted by clinto
I told a bike store guy I needed a 27" wheel and took home the one he sold me, but at home I realized that it's a 688mm, not 27". It seems a little off, but technically it should only be off by a 1/10 inch at most. Is that a big difference? Will it still work? Should I even try or should I take the wheel back?
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11-24-04, 12:15 PM
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Originally Posted by dafydd
Dude, The wheel will probably shrink a little once you put some weight on it and ride it, which was probably factored into design. shrinkage may be worse in cold weather, however...
11-24-04, 12:18 PM
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Originally Posted by T-Mar
Refer to https://www.sheldonbrown.com/tire_sizing.html for a good explanation of tire sizing standards.
11-24-04, 09:44 PM
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Originally Posted by sydney
Dude.....This is just so wrong.
Last edited by dafydd; 11-24-04 at 09:50 PM.
