Discussion in 'Bicycle Mechanics and Repairs' started by Maz, 12 Apr 2010.

  1. Maz

    Maz Legendary Member


    Got back to my bike to go home from work and found the tyre like this:
    Really wierd. The ride in was fine.

    How could this happen?! It had a 'star'-shaped puncture where the gap is. Puncture on inner tube was about 10mm wide at its worst point (repairable or bin it?).

  2. andrew_s

    andrew_s Guru

    You probably had the tube pinched between the tyre bead and the rim.

    The pinched bit of tube will eventually get enough air in to start lifting the tyre away from the rim, at which point air gets in faster, and a big bubble grows on the outside of the tyre and then explodes. The shock of the tube bursting will often lift the tyre over the rim. The interval between fitting the tyre and it going bang is usually quite short, but can be many days.
  3. Gerry Attrick

    Gerry Attrick Lincolnshire Mountain Rescue Consultant

    Is the bike parked in a shed which gets very hot in the sun?
  4. OP

    Maz Legendary Member

    No it is locked to the railing you can see behind it, in the open air.
  5. OP

    Maz Legendary Member

    Only one day, in my case (tyre fitted at weekend). Thanks for the explanation.
  6. Gerry Attrick

    Gerry Attrick Lincolnshire Mountain Rescue Consultant

    Then I'd tend towards Andrew's theory.
  7. That's what we call 'operator error';)
  8. dan_bo

    dan_bo How much does it cost to Oldham?

    I had one of them yesterday after lots of braking down a big hill-rim heated up the pinched inner tube and bang!

    Brown trouser moment.
  9. 02GF74

    02GF74 Über Member

    I often wonder what is the best way to brake down a hill and my theory goes like this - and applies to motor vehicle brakes too.

    Instead of keeping steady pressure on the brake, give it more welly so that it slows you down more that it would. This will heat up the brake components more but then due to Newton's law of cooling, heat transfer is proportional to temperature difference so you loose more heat - rememeber you have heated the compontnets more than you would have done.

    You then roll on a bit, allowing the braking system to cool in the air and repeat so that your average speed of descent is the same as if you were constantly on the brakes but done in jerks.

    good or BS?
  10. MartinC

    MartinC Über Member

    O2 - yes, that's the theory on big hills - repeated hard braking rather than continuous minimises the heat build up. This goes back to the days when people were trying to avoid melting the glue on their tubs.

    I always buy good quality inner tubes, I'm sure cheapo ones are more likely to blow when they overheat. I've seen cheap tubes that have blown on steep descents - large holes where thin parts of the tube have disappeared.
  11. upsidedown

    upsidedown Waiting for the great leap forward

    The middle bit
    My Conti Contacts blow off the rim if i go anything above the maximum stated presure of 85psi, it's happened a few times now where i've given it an extra couple of psi on a Sunday afternoon.
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