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27" / 700c?

Discussion in 'Bicycle Mechanics and Repairs' started by bonj2, 13 Aug 2007.

  1. bonj2

    bonj2 Guest

    I thought the two were synonymous, but i bought an inner tube that was described as being for 27" wheels and had to take it back for a refund 'cos there was far too much of it - when it was in all round, it was bunched up in places!
    My wheels are definitely 700c.
    Is 27" a different size to 700c then? Or was it just a faulty tube?
     
  2. Noodley

    Noodley Guest

    I thought 700c fitted 29" wheels

    (edit - here you go: http://sheldonbrown.com/tyre-sizing.html)
     
  3. Chuffy

    Chuffy Veteran

    <sits back and waits for Bonj to 'prove' Sheldon wrong> ;)
     
  4. papercorn2000

    papercorn2000 Senior Member

    So you "thought" something and were wrong?

    Hmmmm. I think you'll find very few people are surprised!
     
  5. hubgearfreak

    hubgearfreak Über Member

    you can't fit '700' (622mm) tyres to 27" (630mm) rims, or vice versa.

    but an inner tube for either would fit either...
    indeed many inner tubes are labelled up as for both
     
  6. rustychisel

    rustychisel Well-Known Member


    game, set, match, eh?:biggrin::biggrin::biggrin::biggrin:
     
  7. OP
    OP
    bonj2

    bonj2 Guest

    hmmm.. this must have been a faulty tube then, 'cos it was FAR too baggy and bunched up. it was as if it was for a 29" wheel, but it definitely wasn't 'cos it said 27" on it..
     
  8. OP
    OP
    bonj2

    bonj2 Guest

    this is knowhow forum. Technical discussion only. If you don't know the answer to the question then button it.
     
  9. hubgearfreak

    hubgearfreak Über Member

    hmmm.. this must have been a faulty tube then, 'cos it was FAR too baggy and bunched up. it was as if it was for a 29" wheel, but it definitely wasn't 'cos it said 27" on it..[/QUOTE]

    a '29" ' wheel is still a 622mm.
    just a wider tyre & probably rim.
    you did read that sheldon brown link, didn't you?

    perhaps you got one that was far too wide?
    if you're tyre is 25-622 or 27x1, then a 622-37 or 27x1 1/4 tube will be too big.

    maybe, just maybe, it's your fitting abilities at fault?
     
  10. OP
    OP
    bonj2

    bonj2 Guest

    maybe? it did say 27" x 1.25". My wheel is 700c x 23. It was still massively too long though, rather than too wide to fit in the tyre.

    Can you explain how all the fitting ability in the world is going to be able to make some rubber vanish into thin air, magically making it shorter? I can fit all other tubes fine.
     
  11. OP
    OP
    bonj2

    bonj2 Guest


    ah, yes - well that does explain why the one i bought didn't fit, but it's quite confusing:
    in the 'french' sizing section, it lists 700c as ISO 622. That explains why the tube I got which was 27" x 1 1/4" was too big, as 27" by anything is ISO 630.
    But 28 x 1 5/8 x 1 1/4 is ISO 622! eh?! 28 > 27, but 622 < 630... hmmm, very odd.
    I think it's the black magic associated with the width and diameter not being entirely separate...


    he does explain it as well as it could be explained though, so I know in future only 28" x (two fractions - why there's two god knows), 28" x 1 1/2 'canadian F.13', or 29" will fit...but I think i'll stick to ordering 10packs of 700c x 18-23 from crc in future rather than getting some dodgy fractional size one from wilkos...
     
  12. OP
    OP
    bonj2

    bonj2 Guest

    i'm upset that sheldon hasn't managed to find a place on his webpage for the 26"x2.6" beast i've got on the back of my MTB... :sad:;)
     
  13. Chuffy

    Chuffy Veteran

    That's because he deals with bikes, not tractors. :sad:
     
  14. hubgearfreak

    hubgearfreak Über Member

    maybe? it did say 27" x 1.25". My wheel* is 700c x 23. It was still massively too long though, rather than too wide to fit in the tyre.[/QUOTE]

    there's the problem then.
    1 1/4 is around 32mm, not 23, which is the size of your tyre*

    the nominal outer diameter of your tyre is 622 + 23 +23 = 668
    whereas the nominal outer diameter of a 27 x 1 1/4 is 630 + 32 + 32 = 694
    had you been fitting it to the correct width tyre for that tube, ie 32x622 then the nominal outer diameter would have been 686. it will work every time

    you'll just have to believe me that 27x1 1/4 and 32x622 (700x32) tubes are interchangeable

    *to save further confusion for you, the wheel is the metal thing, tyre the rubber thing that goes on the outside of the wheel
     
  15. Noodley

    Noodley Guest

    C'mon give bonj a break.

    This is Know How. It should be devoid of personal jibes.