100psi = BANG?

Bunneh
Bunneh Posts: 1,329
edited February 2010 in Workshop
I signed up here ages ago and only just uncovered the site again, oopsies!

Yesterday I decided to take myself out on a spin, usually around 10 miles of local country and the like. It was raining but I prefer the rain, there's less cars and no morons on the streets. Anyhoo the noise we all dread came into my ears, 'hsssssssssssss', crapsticks... I slow and moan to myself when I realise I have everything I need to repair it bar the sodding pump, which was still in my other rucksack. Chunnering I start the walk home, the rain had slowed to a trickle so it wasn't a bad walk back, just I would have prefered riding it.

I get home and set about repairing it; I was expecting a snakebite because Bolton council seem to have forgotten how to repair the major roads, but are perfectly happy to spend millions on statues and new council housing. Anyway, it wasn't a snakebite but rather a large thorn. I repair it anyway, as you do just in case you need one, and fit a brand new tube and one of the new tyres I'd bought a few weeks previous. Now I personally always run on 100psi, it's hard enough and has a little bit of squish to aid my grip; so there I am pumping away, hit the 100psi and stop. I turn around to check what the cat is doing and I hear this creaking sound...

BANG!

Inner tube explodes, firing half the tyre off the rim and sending fishy air everywhere, scaring the crap out of me, the cat and several small families in India. I chuckle to myself because it was mildly amusing but it got me wondering; was I wrong about the PSI all along?

I have always run on 100psi, never had a problem; should I return the tube or was it just my error? The box didn't indicate what the best PSI was and the way the tube blew I think it may have been defective, split right a long the seem.

Ideas?

Ta!
http://www.youtube.com/user/Eurobunneh - My Youtube channel.

Comments

  • Monty Dog
    Monty Dog Posts: 20,614
    You had probably trapped the inner under the tyre bead which caused a localised weakness and the bang. Lightly inflate the inner when fitting and check it isn't trapped before inflating.
    Make mine an Italian, with Campagnolo on the side..
  • sungod
    sungod Posts: 16,529
    the psi rating that matters is the one usually embossed/printed on the tyre sidewall

    the tube is just there as an airtight liner for the tyre and doesn't have a pressure rating

    the tyre 'supports' the tube enabling it to hold the required pressure, the tube alone could never hold anything close to 100psi

    as monty dog says, it sounds like you pinched the tube - or perhaps didn't seat the tyre on the rim so the tube can balloon in the gap
    my bike - faster than god's and twice as shiny
  • balthazar
    balthazar Posts: 1,565
    It all happens in a fraction of a second. if you had a high framerate video camera on it, you could play the video back slowly to see the tyre lift from the rim, the tube escape through the gap, expand outside the tyre, then – BANG – explode like a ballon; then retract back through the gap, allowing the tyre to seat itself again on the rim. That's why the tube is split along the seam; often they have ragged holes as a result of these blowouts.
  • crankycrank
    crankycrank Posts: 1,830
    Agree with Monty Dog and sungod with the pinched tube theory being the most likely cause. Did you check the puncture area of the tyre during inflation. It could be that the thorn caused a big enough hole that the tube ballooned through the cut and ruptured. Could also be that the tube was defective and had a weak spot that burst which has happened to me a couple of times. Also, make sure your pressure gauge hasn't suddenly failed giving a false low reading.
  • balthazar
    balthazar Posts: 1,565
    crankycrank wrote:
    Agree with Monty Dog and sungod with the pinched tube theory being the most likely cause. Did you check the puncture area of the tyre during inflation. It could be that the thorn caused a big enough hole that the tube ballooned through the cut and ruptured. Could also be that the tube was defective and had a weak spot that burst which has happened to me a couple of times. Also, make sure your pressure gauge hasn't suddenly failed giving a false low reading.
    So do I — there's no dispute; I just expounded on what happens as a result of a tube trapped in the bead. I don't think it could have been a faulty tube – if there was a bang, then it happened outside the tyre.
  • dennisn
    dennisn Posts: 10,601
    balthazar wrote:
    crankycrank wrote:
    Agree with Monty Dog and sungod with the pinched tube theory being the most likely cause. Did you check the puncture area of the tyre during inflation. It could be that the thorn caused a big enough hole that the tube ballooned through the cut and ruptured. Could also be that the tube was defective and had a weak spot that burst which has happened to me a couple of times. Also, make sure your pressure gauge hasn't suddenly failed giving a false low reading.
    So do I — there's no dispute; I just expounded on what happens as a result of a tube trapped in the bead. I don't think it could have been a faulty tube – if there was a bang, then it happened outside the tyre.


    Could also have been an improperly seated tire bead.
  • balthazar
    balthazar Posts: 1,565
    dennisn wrote:
    Could also have been an improperly seated tire bead.
    'tis true.
  • Bunneh
    Bunneh Posts: 1,329
    Sorry for my slowness of reply, tend to let my questions sit for a while :)

    Certainly sounds like what you suggest and I must admit I had forgotten about that sort of thing. I fitted a new tube earlier and checked around the rim this time, no problems. Went on a lovely ride over the hills; so thanks ever so much for the info!

    /hugs
    http://www.youtube.com/user/Eurobunneh - My Youtube channel.

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