27" / 700c?

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?
 

Noodley

Guest
I thought 700c fitted 29" wheels

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

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
 
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bonj2

Guest
hubgearfreak said:
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
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..
 
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bonj2

Guest
papercorn2000 said:
So you "thought" something and were wrong?

Hmmmm. I think you'll find very few people are surprised!
this is knowhow forum. Technical discussion only. If you don't know the answer to the question then button it.
 

hubgearfreak

Über Member
bonj;39772][QUOTE=hubgearfreak said:
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
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?
 
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bonj2

Guest
hubgearfreak said:
perhaps you got one that was far too wide?
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.

hubgearfreak said:
maybe, just maybe, it's your fitting abilities at fault?
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.
 
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bonj2

Guest
hubgearfreak said:
you did read that sheldon brown link, didn't you?

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...
 
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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:;)
 

hubgearfreak

Über Member
bonj;41079][QUOTE=hubgearfreak said:
perhaps you got one that was far too wide?
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
 
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