Got a puncture, but don't know how...

Discussion in 'Bicycle Mechanics and Repairs' started by Maz, 30 May 2008.

  1. Maz

    Maz Guru

    Went back to the bike to go home and noticed straight away I'd got a flat.

    Took off the wheel and inspected the tyre inside and out...couldn't for the life of me see any holes in it (it's got some kevlar lining stuff, so seems to be doing its job). Checked the inner tube and it wasn't obvious where the puncture was. Anyway, I put the spare inner tube on and re-fitted.

    When I got home I checked the old inner and the puncture was right at the base of the valve...not repairable. I can't figure out how I got a hole in that place.

    Anyone had a puncture like this? What might have caused it?
  2. Steve Austin

    Steve Austin The Marmalade Kid

    Happens a lot on MTB tyres. Caused by inner moving within the tyre and the inner catching on the sharp edge of the hole in the rim.

    Check the hole for burrs.

    Can happen more often under heavy braking when the tyres not inflated very much. not very common tbh, just unlucky
  3. OP

    Maz Guru

    Thank you, sir. I will look for any sharp edges etc near the hole.
  4. RedBike

    RedBike New Member

    Beside the road
    It can also happen when you're inflating the tyre. The pump pulls the tube.
  5. Odyssey

    Odyssey New Member

    Yeah, what the others said. I've had loads over the years. Even occasionally ripped the valve right off.
  6. Mister Paul

    Mister Paul Legendary Member

    You're better off using a track pump. Using a hand pump that fixes straight onto the valve will pull it backwards and forwards as you pump unless you're very careful. And over time this can wear through the inner tube.
  7. briank

    briank New Member

    It's also a natural place for a weakness in the manufacturing process to show up. After all, the rest of the inner tube is just a big, thin, continuous doughnut of rubber, but the integrity of the whole thing is compromised by shoving a valve through it. All the rest about pumping up roughly etc is true, but it's still a natural point of weakness and sometimes the tube just fails there. There's virtually no chance it was a real puncture.
  8. Crock of Gold

    Crock of Gold Guest

    Sounds like what I got last Sunday.:smile:
  9. Joe24

    Joe24 More serious cyclist than Bonj

    I've had them go at he valve before. 3 of them. I pulled the pump off(track pump) and with my heavy handedness i pulls the valvle down slightly and tore it. 120psi going unexpected when my hand was there was a huge shock :smile:
  10. Globalti

    Globalti Legendary Member

    You probably already had a small hernia....
  11. Bigtallfatbloke

    Bigtallfatbloke New Member

    That is where most of my punctures happened...the valve (presta) moved around to much when I pumped up the tyre and the rubber slit where it joins the valve
  12. CopperBrompton

    CopperBrompton Bicycle: a means of transport between cake-stops

    You can also just get duff tubes. I had one recently where the tube suddenly (and noisily) deflated while the bike was sat in my hallway. Nothing found in the tyre, but a big rip in the tube.

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