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Whilst mending G/Sons puncture on his Mountain bike yesterday, I discovered something that struck me as odd. When inflated just enough to form it's shape the inner-tube was 38" in diameter! although the bike is classed as a 29er, (which I assume is the wheel Diameter). Wrong tube in the tyre was my first impression, but it was a brand new bike last xmas, so obviously had been fitted by the manufacture's. Why would they use a tube so much bigger than the wheel, when fitted it needs to be heavily convoluted to get it in the tyre? - strange!
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That's very odd. I've never seen a tube that wasn't the 'right' size.
But some people have -
forum.cyclinguk.org/viewtopic.php?t=59745
which doesn't explain why yours was there from new.
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Interesting! - Maybe the makers used a "refurbished" wheel that somebody else had repaired! ?
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New one to me I'm afraid.
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The very odd thing is that the largest wheel you can get for a normal bike is 29".
Though of course people do still make Penny Farthings with various wheel sizes, so maybe the tube was meant for one of those.
What markings are on the tube?
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Actually none that I noticed! - and its back in, holding Air and he's happy again, so I'm not going to un-coil it to find out ;-)) - next time it's out I'll check and chuck it, and get a smaller one! ;-)
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But is it the right size when uninflated and just laid flat against the tyre?
I've often noticed that with car tubes - inflating them outside the tyre just enough to form their shape sometimes appears to make them too big for the wheel. Not quite to your extend, but the effect is there.
I would guess it is normal, and what's happening is the rubber is stretching preferentially in the dimension that offers least resistance. Constrain it inside the tyre and it will only inflate enough to fill the space.
A bit like balloons that sometimes go into absurd shapes and have to be massaged to turn into their intended shape. It sometimes seems as if the first bit to inflate could easily become over-inflated before it reaches the far end.
I've noticed the effect with tyres because it's easier to get the tube inserted if it has a bit of air in it, and also to avoid damaging it with the tyre lever (alias screwdriver). But it does sometimes mean there is too much tyre to stuff into the gap.
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When mountain biking I always carry a spare tube and a folding tyre in case of shredding one in an inconvenient location. They are such fun when your fingers are frozen and the light is going...
:-(
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Yes, without the tyre constraining it, one can quickly inflate the inner tube to a far greater size than the tyre in which it is destined to go. The rubber compound of the inner tube is far more flexible than the tyre carcass. This also enables one inner tube to fit a variety of tyre sizes, reducing the amount of stock the bike shop needs to carry.
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>> Though of course people do still make Penny Farthings with various wheel sizes, so maybe
>> the tube was meant for one of those.
Penny farthings with pneumatic tyres?
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And the first link has a 36" wheel! - I wonder......!
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one for Humph! - Manatee
