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Thread: Flats

  1. #1
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    Flats

    So yesterday I blew out my eighth valve stem in about two and a half months. Im at my wits end with this problem. In the fifteen years I have been mountain biking I have hardly ever had issues with flats and now all of a sudden I cant go on a ride without getting one. I have to assume its my rim since it is the same place every time but what could have changed? This is not my first season on these rims and I am running the same tire pressure that I have always run. Im running Easton XC two rims with a rigid fork. Any insight or ideas would be greatly appreciated as this has become very frustrating and expensive at this point.

  2. #2
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    sounds to me like you hit the nail on the head. switch the wheel. or at least borrow a spare from a friend to test your theory. hope you get it worked out soon!

  3. #3
    nodejitsu
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    A friend a mine had same issue, it was the rim, Bontrager rims to be exact. He has to use Bontrager tubes. The Specialized tubes he was getting because that's what they have the shop closest the trails are like too thick because of the shape/offset of the Bontrager rims combined with the tubeless strip that came in them.

    Try switching tubes.

    And also check if there is a strip inside for tubeless ready and remove it or replace it with one that is not for tubeless and not as thick.

  4. #4
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    Are you piercing the tube near the valve stem or physically breaking valve stems? I would take the tire/tube off and check out the valve hole for burrs or a sharp edge. If present, then I would consider using a cone shaped dremel bit to smooth out any sharp spots. Also check you rim tape/strip condition. I have had bad rim strips cause flats. I have also used portable frame pumps like a maniac and damaged the stems.

  5. #5
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    Yeah, the valve stem keeps ripping at the base. It has happened with two different brand of tubes now, the only two brands any of the shops around here carry. I rotated my rim strip and put a new, smaller hole in it for the stem to go through but no luck. I guess my next step will be to file down the edge of the hole, beyond that I cant think of what could be the problem. This is my second season on these rims, I didnt flat at all last season and like I said above, never really had a problem with flats before so Im pretty much perplexed at this point.

  6. #6
    nodejitsu
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    Bogus.

  7. #7
    The White Jeff W
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    Does your tire come on & off easily? It might be slipping on the rim under power & taking the stem with it.
    No moss...

  8. #8
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    If you use presta valves try leaving the lock nut off.

    Tim

  9. #9
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    Quote Originally Posted by Wombat View Post
    If you use presta valves try leaving the lock nut off.

    Tim
    This is something that crossed my mind. Perhaps I am tightening it down too tight?

  10. #10
    bt
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    I've never used the lock nut on a bicycle.

  11. #11
    29er
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    Tubeless

  12. #12
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    Had this happen twice with house brand tubes from Performance, separated at base of stem, another looked like it was already repaired(no wonder they were on sale). Bought some Bontrager tubes, no problems since, like the 48mm stem length better anyway.

  13. #13
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    If the valve stem is tearing at the base, you're either putting the knurled nut of way too tight, or your tire is rotating on the rim under braking power.
    The nut, if you use one at all, should only be 1/4 to 1/2 turn past when it touches the rim. If your tire is rotating, you need to use more air pressure or try a tire that has a tighter fitting bead like Continental, Bontrager, etc.

  14. #14
    ballbuster
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    Quote Originally Posted by bt View Post
    I've never used the lock nut on a bicycle.
    Me neither. I'm not sure what that locknut is for. I mean, when I mount the tire, I always push the stem in anyway to pull the tube away from the rim and tire where it likes to pinch during assembly. You can always push the stem through the tire back into the air chuck anyway.

    And I'm finding tubeless sucks. I chase more flat tire issues now that I switched my FS bike to tubeless. I'm going back to LunarLites. When I was on tubes, I would flat once a year or so. Now, I have to mess with my tires before every ride... I mean, even beyond the normal preflight checklist of topping the pressure up a bit.

    I had issues where my rim would wear a small hole in the stem, or the part of the tube where the stem is molded on. I used a small tiny strip of Velox cloth rim tape, cut a small hole in it (smaller than the stem) and forced the stem through it so it would be a tight fit. Problem went away. Now, I do this on all my tubes.

    I would also suggest taking the tire and rim strip off, and take a small round fine file to the edge of the stem hole. Feel for any burrs, and round them off.
    Last edited by pimpbot; 08-23-2012 at 04:41 PM.

  15. #15
    West Chester, PA
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    Quote Originally Posted by pimpbot View Post

    And I'm finding tubeless sucks. I chase more flat tire issues now that I switched my FS bike to tubeless.
    You're either doing it wrong or your setup sucks. Just sayin.

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