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  1. #1
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    low pressure ripping valve stems...help

    my bud has a stock pug with large marge no cut outs.. there is about 280 lbs on the bike. going through tubes.. all ways the valve stem getting chaffed til a leak..
    tubeless? what about the "burp"? 2 presta nuts on the tube, one on the inside of the rim and one on the out side?
    he is really discouraged right now so a good fix is bady needed..
    thanks a lot!!!
    Boz

  2. #2
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    Rough edge on the rim?

    What tubes and pressure is he running?

  3. #3
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    He needs a thin layer of tape between the tyre and the rim at the bead seat. The tyre is too loose and is sliding on the rim.

    Some talcum powder between the tyre and tube may also help.

    edit...two nuts on the valve stem (inner and outer) won't help.
    I see hills.

    I want to climb them.

  4. #4
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    does the valve stem get angled through the hole because the rear tire is slipping during climbing? If that is the case, you can either add layers of 1" gorilla or some other tape over each of the bead seats for a tighter fit of the tire, or glue one side of the tire bead to the rim to prevent slipping. With glue, not the whole perimeter is needed just a few spots. Something like shoe goo or a rubber cement. One side only so you can change tubes will still prevent slipping.

    If this is a front tire there is something else going on unless there is some severe downhill braking on very grippy surfaces. Is there a possibility that the hole is too big in the rim? (schraeder hole for presta valve) Or is he inflating it using a hand pump fairly often and bending the valve from side to side repetitively?

  5. #5
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    Third vote for tape around the bead seat of the rim to make a tighter fit, or cement the tire to the rim to prevent it from rotating at low pressures.

    It could happen even with a front tire because of precession: Precession (mechanical) - Wikipedia, the free encyclopedia

  6. #6
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    I've had it happen on the front of my 29er before. Braking forces I put it down to.
    I see hills.

    I want to climb them.

  7. #7
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    Unfortunately you can get precession of the tube even with a glued tire. I have had the tube fold over itself at the valve stem even though the tire was glued. Gluing will stop the tire slipping and dragging the tube with it, so still worth doing but may not totally solve the prpblem.
    Latitude 61

  8. #8
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    Also, try removing the valve nuts. This allows the tube to move without putting pressure where the value and tube join.

    Tim

  9. #9
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    I agree with Wombat. With the valve nut tight against the rim, when the tire slips it will try to rip out the valve stem out of the tube. I either leave the nut off or just spin them up until they butt up against the valve cap, on both my dirtbikes and mountain bikes. I've had many instances where I can see the tire slipped, and the valve stem is at an angle, but I was able to realign it without any flats or issues.

  10. #10
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    Using talcum powder seems to have gone out of fashion, but it's what I've always used - very liberally on the fatbike - and I don't get this problem.

    I suspect the rider is using a tyre pressure too low for his weight. It may be time for rim locks - does anyone make something suitable for fatbikes?
    As little bike as possible, as silent as possible.
    Latitude: 5736' Highlands, Scotland

  11. #11
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    I still use talcum powder. I think it helps with letting the tube settle in a more "natural" state inside of the tire and also to avoid the tube folding over itself during inflation. Tears at the valve stem however stem from the tire slipping on the rim itself, at least from my experience.

    Quote Originally Posted by Velobike View Post
    Using talcum powder seems to have gone out of fashion, but it's what I've always used - very liberally on the fatbike - and I don't get this problem.

    I suspect the rider is using a tyre pressure too low for his weight. It may be time for rim locks - does anyone make something suitable for fatbikes?

  12. #12
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    I went through quite a few tubes a year ago figuring this out on the rear of a beater SS. Tire is slipping on the rim. Talc, 2 nuts, no nuts are probably not perfect solutions as I tried them all with marginal success and longevity before the condition returned. New tire with tighter beads and/or building up the rim shelf with some tape are the best bets.

  13. #13
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    Quote Originally Posted by Stevob View Post
    He needs a thin layer of tape between the tyre and the rim at the bead seat. The tyre is too loose and is sliding on the rim.

    Some talcum powder between the tyre and tube may also help.

    edit...two nuts on the valve stem (inner and outer) won't help.

    I agree - talc the inside of the tire and once the tube is pumped up - throw the nuts away. I'm also a big boy riding a Pugs with LM and did rip out the stems on two tubes. That was a year ago or more.

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