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What exactly is a 'pinch puncture'?

Discussion in 'Bicycle Mechanics and Repairs' started by tomb1960, 9 Sep 2007.

  1. tomb1960

    tomb1960 New Member

    Location:
    Birmingham
    Is it when you hit an egde (eg a pothole) at speed and your poor inner tube is pinched momentarily against the rim? I ask as I had two otherwise unexplained rear punctures on my run this morning (unexplained in that the tyre seemed totally un broached) one was definitely seconds after hitting a pothole at speed. This did effect my enjoyment somewhat negatively. How are they best avoided, and are some brands of inner tube more prone to it than others?
     
  2. simoncc

    simoncc New Member

    That's what I've always understood them to be. The best way to avoid them is to keep your tyres pumped up properly and not to bump up kerbs, especially if you are on a bike with thin tyres. Buy a decent track pump with a pressure gauge.
     
  3. Peter

    Peter Senior Member

    They are normally caused by potholes. A combination of speed & weight (in my case!) Sometimes the inner tube isn't sitting on the rim properly when pumped up. I was on the Southern Sportive at Petersfield today and suffered exactly that - 12 miles from the finish, much to my disgust.
     
  4. Keith Oates

    Keith Oates Janner

    Location:
    Penarth, Wales
    Sometimes you get the same 'damage' from grill type drain covers if you hit them longitudinally!!!!!!!!!!!!!!!!!!!!!!!!
     
  5. bonj2

    bonj2 Guest

    Yes.
    Also known as a snakebite (that's what I call them), the tell-tale sign of one is two slits parallel to each other running along the tube about a centimetre or so long and just under an inch apart, although the dimensions can obviously vary.
    They are much more common when MTBing...I've only once had one on a road bike and that was when I was 'amber-gambling' on a downhill stretch of (typically bad) road.

    Oh well we can't have that! The thing to do is recognise that it's inevitable, it happens to the best cyclists and the best bikes, there's not really that much you can do about it, the way to minimise the 'negative effect on your enjoyment' as you so eloquently put it is just to feel slightly proud having successfully changed it.



    Basically try to avoid potholes at speed, and have high pressure in tyres.
    Other than that there isn't that much you can do.
    All inner tubes are just rubber tubes, you can't really get a snakebite-proof tube. I think nokian do a downhill tube that is made of really thick rubber that is less susceptible to it but it weigh about a kilogram, costs about seven quid and is for 26" MTB wheels, I wouldn't even think it'd be worth it on my MTB and i get the odd snakebite now and again.
     
  6. tomb1960

    tomb1960 New Member

    Location:
    Birmingham
    Thank you, I like the snake-bite analogy that's exactly what it looked like. I was quite proud of how slickly I changed the inner tube particularly the second time!