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My tyres keep deflating but I don't have a puncture...

Discussion in 'transport' started by Orang Utan, Oct 7, 2010.

  1. Orang Utan

    Orang Utan like an outdated combine harvester

    ...it must be the valve, but why does this keep happening?
    i must be doing something wrong. i must be mistreating the valve when i inflate it or putting the inner tube in wrong.
    how do i work out what i'm doing wrong?
     
  2. TitanSound

    TitanSound Mr Beardy Drummer

    HTH!
     
  3. 100% masahiko

    100% masahiko i is a professor and is magical like totoro

    Have you changed the innertube?
    And how do you know it's not a puncture?

    When you change innertube, do you clean the rim area and the inside of the tyre with a wet cloth?
     
  4. Orang Utan

    Orang Utan like an outdated combine harvester

    yes, of course, that's how i know it's not a puncture - when i pulled the last one out, there was nothing wrong with it.
    i checked the rim and tyre under a strong light and there's no grit or anything.
    i've had about 5 punctures in a month, but i've always had problems with tyres deflating slowly on this bike, having to pump them up 2 or 3 times a week.
     
  5. Orang Utan

    Orang Utan like an outdated combine harvester

    huh?
     
  6. tommers

    tommers I did it!

    stupid question but have you checked the tube by sticking it under water?

    What type of valve is it?

    If it's a presta valve

    [​IMG]

    then there will either be a tear at the base or a bent valve bit.....
     
  7. editor

    editor Got a fever +the only prescription is more cowbell

    Have you tried taking the tube off the bike, inflating it and lobbing it into a bath/basin full of water and giving it a sexy squeeze and looking for bubbles? It's always worked for me!
     
  8. Orang Utan

    Orang Utan like an outdated combine harvester

    it's a presta, yes!
    i suppose i shall have to have a look at the old tube tomorrow under water (shudder) but i have noticed the valve is often bent - they're fragile mechanisms.
     
  9. tommers

    tommers I did it!

    Oh Ok, yeah if the valve is bent then it'll leak air. You need to have a less enthusiastic pumping action. ;)

    Do you have a pump that locks on to the valve?

    Check it under water though anyway.
     
  10. TitanSound

    TitanSound Mr Beardy Drummer

    Well generally if there is no puncture then it is the valve at fault. You stated you did not have a puncture so I quoted your own diagnosis and helpfully added "Hope that helps" in internet format.
     
  11. Crispy

    Crispy Fond of drink and industry

    Do you use a track pump? A bent valve is usually due to over-enthusiastic thrusting with a hand pump.
     
  12. 100% masahiko

    100% masahiko i is a professor and is magical like totoro

    I had a similar problem where I was getting 2-3 slow punctures a week.
    I would change the inner-tube and after a bike ride it was fine.
    Then overnight the tyre would be flat.
    I tried everything. Checked rims, clean the inner tyre and couldn't work it out.
    The water test showed nothing.

    Solution came when I changed the actual tyre and kept the pressure between 110 and 120 psi.
    No problems since - and it's been months now...
     
  13. Lemon Eddy

    Lemon Eddy Disliked by dwyer

    Find out which of your co-workers you pissed off and tell them if they let your tire down again you'll end them, badly.
     
  14. Orang Utan

    Orang Utan like an outdated combine harvester

    yeah, maybe it's damaging the valve? how do i prevent this?
     
  15. Orang Utan

    Orang Utan like an outdated combine harvester

    i only ever use a track pump - can never get enough air in with hand pumps
     
  16. Orang Utan

    Orang Utan like an outdated combine harvester

    not much help then is it? :p
     
  17. Orang Utan

    Orang Utan like an outdated combine harvester

    i need new tyres/wheels anyway :)
     
  18. turing test

    turing test Nearly Toowrong

    When I lived in Texas we would get thorns in our tyres which were nearly impossible to find or remove. Naturally they led to holes in the tube which were nearly impossible to find-even using water. These punctures would sometimes deflate the tire in a day or two, or even stop leaking at low PSI.

    I have a fairly new tire right now which I am afraid has glass fragments I can’t find-although in that case I could pretty easily find the holes in the tube, and go backwards to find the glass embedded the tyre.
     
  19. gentlegreen

    gentlegreen ¡Nadie espera a la babosa española!

    I'm now firmly of the track pump persuasion too - after finding I had been seriously under-inflating my tyres for 20-odd years :eek:

    I've never managed to damage a presta valve with a hand-pump though. It's a case of the angle of approach and stabilising it with your left hand at the valve end against the wheel.

    I always push the valve first with my finger before I pump to make sure it's free and to blow out any crud.
     
  20. Orang Utan

    Orang Utan like an outdated combine harvester

    i got a 'puncture' on the way back from work, got out a hand-pump and promptly ripped the valve clean out of tube. had to walk home from chelsea.
    getting fed up of this. surely something must be wrong if i can't cycle for 8 miles without the back tyre deflating?
    i replaced the inner tube with the old one and it's nicely pumped up, though i couldn't fasten the washer onto the valve to keep it in place, so it'll probably last just one ride. will probably deflate overnight anyway. this is shit. i can't afford not to ride this week. :(
     
  21. gentlegreen

    gentlegreen ¡Nadie espera a la babosa española!

    Ordinarily one would pump up the removed inner tube to see where the puncture is, and place it against the tyre so that any remaining bit of glass or whatever can easily be found and removed.

    Difficult to do that with no valve though. :facepalm:

    The other main causes of punctures are protruding spoke ends / thin rim tape, or pinching the inner tube while re-fitting the tyre - but it sounds like you are being very rough when pumping up the tyre - and with no nut clamping the valve to the rim, it's going to be that much easier to tear a hole there.

    Sounds like you may need to look out for bicycle maintenance classes ...

    You can get compact pumps with flexible hoses...
     
  22. weepiper

    weepiper eb slootly non verbal

    yeah what gg said... when you pump it up keep your non-pumping hand around the back of the pump head and sort of brace it against the spokes so you're not moving the valve around so much. Presta valves are a bit fragile. If you regularly find you're buggering up the valve then take your bike to your LBS and ask them to drill the valve holes out to take a schraeder valve tube as they are a bit harder to damage by over zealous pump action.

    Otherwise, get a stanley knife or sharp penknife and sit with the tire, go right round the OUTSIDE of it and dig the knife gently into any little cuts or slits, pounds wil bet you peanuts there's a tiny 3mm shard of glass hiding in one that you won't be able to feel from the inside of the tire but when the tube's pumped up hard is just enough to make a teeny hole.
     
  23. Orang Utan

    Orang Utan like an outdated combine harvester

    i don't have a puncture though! it's just this shitty valves. i'm sure they've got flimsier in recent months. you shouldn't be able to rip out a valve so easily, or even damage it so easily. i'm gonna have to go in to a shop and get them to watch me change a tube and see where i'm going wrong.
     
  24. weepiper

    weepiper eb slootly non verbal

    try a different brand of tube?
     
  25. Lemon Eddy

    Lemon Eddy Disliked by dwyer

    This. Because OU, you're right - you should not be able to rip valves out. I'm a hammering clumsy idiot and I've never managed that trick, just by being moderately careful. either you've bought a job lot of the shittest tubes in existence, or you've got a problem with the wheel. For instance, is there any form of sharp metal near the valve hole that could be cutting the tube at that point?

    The way you describe your recurring punctures does suggest there is a piece of sharp debris stuck in the tire, or you have a spoke problem. The next time you have a flat you need to take the tube out, gently inflate it, and find where the leak is.
     
  26. Orang Utan

    Orang Utan like an outdated combine harvester

    there are no leaks though - so no puncture - it MUST be a valve problem
     
  27. Orang Utan

    Orang Utan like an outdated combine harvester

    you kind of get what you're given at my local bikeshop :(
     
  28. weepiper

    weepiper eb slootly non verbal

    seriously... if it's a very slow puncture you won't get air escaping when you have the tube slightly pumped up to check it underwater, only when it's pumped up to pressure inside the tire.
     
  29. Gromit

    Gromit International Man of Misery

    Tyre mites.

    Little insects that hide inside your tube and eat the air.

    You need a tyre mite exterminator who will bring trained spiders to enter your tyre and track the little blighters down and eat them.

    HTH.
     
  30. turing test

    turing test Nearly Toowrong

    Word!
     

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