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  1. #1
    Peace and bicycle grease! une_vitesse's Avatar
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    strange tube failure

    when we do tube changes at our shop, we inspect the old tube to try to determine the cause of the flat. twice or thrice, i've come across something strange: a slit on the inside (rim side, not tire side) of the tube, about 1 cm long, about 1 cm from the valve stem, centered between and parallel to the seams. the rims had nothing out of the ordinary about them (no burrs or scratches), the last one even had a properly installed velox rim strip.
    any other wrenches ever seen this, have any hypotheses?
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  2. #2
    Real Men Ride Ordinaries fuzz2050's Avatar
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    you offended the gods. I've long since stopped trying to understand why flats happen. It's like asking why do bad things happen to good people.

  3. #3
    Senior Member DannoXYZ's Avatar
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    Is the tube significantly smaller than the tyre?

  4. #4
    cab horn
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    Quote Originally Posted by une_vitesse View Post
    when we do tube changes at our shop, we inspect the old tube to try to determine the cause of the flat. twice or thrice, i've come across something strange: a slit on the inside (rim side, not tire side) of the tube, about 1 cm long, about 1 cm from the valve stem, centered between and parallel to the seams. the rims had nothing out of the ordinary about them (no burrs or scratches), the last one even had a properly installed velox rim strip.
    any other wrenches ever seen this, have any hypotheses?
    And who was the person to install said tubes before it went flat and subsequently was delivered to your shop?
    Mes compaingnons cui j'amoie et cui j'aim,... Me di, chanson.

  5. #5
    XR2
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    Senior Member XR2's Avatar
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    Pinched in the bead when inflated.Takes awhile to kill it.
    I owe-therefore I am.

  6. #6
    Peace and bicycle grease! une_vitesse's Avatar
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    Quote Originally Posted by DannoXYZ View Post
    Is the tube significantly smaller than the tyre?
    this last one wasn't: 700Cx23-28 in a 700Cx25 tire. that is a good point, though would you think the over inflated tube would fail at one of the seams, rather between them?

    Quote Originally Posted by operator View Post
    And who was the person to install said tubes before it went flat and subsequently was delivered to your shop?
    i don't know about the previous ones, but the last one was installed by me. the tube was straight in the tire, which i mounted by hand.

    Quote Originally Posted by XR2 View Post
    Pinched in the bead when inflated.Takes awhile to kill it.
    true dat, but my experience with those types of pinch flats leads me to believe that they usually leave a distinctive star shaped hole, and make a big bang at their eventual demise (not the same as the "other" type, aka snakebites which tend to leave two small, parallel, straight slits and take no time at all to deflate)
    come to think of it, a pinch flat caused by having to mount the tire with levers might leave a mark like that. but that too would deflate pretty quickly.
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  7. #7
    Senior Member DannoXYZ's Avatar
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    So this tube with the mystery slit goes flat slowly without a bang? Weird...

    Examine the box the tube came in for cuts from box-cutters... maybe it went through the box enough to nick the tube, but not cut all the way through.

  8. #8
    Charles Ramsey
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    I've seen those. Inflate a tube outside the tire and some of them will have two bulges on either side of the valve stem. There is a stress riser caused by the double thickness of the rubber around the stem and also this area was exposed to heat when the valve stem was installed driving off the plasticizers. Add a bit of valve stem squirm cassed by braking use a tube slightly too small and a bit of dirt and this will be the first place the tube will fail.

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