Why do I keep Pinch Flatting BOTH tires?- Mtbr.com
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  1. #1
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    Why do I keep Pinch Flatting BOTH tires?

    I'm rolling a full rigid 29 Origin 8 with Maxis Ignitor tires 2.10" and Mavic 317 wheels. I am 200 lbs. I generally put 40 psi in both tires. Mostly riding semi-technical terrain (some rock hopping but mostly rolling single track). Does anyone else have this problem or is it just plain bad luck?

    Are certain tire / wheel combinations that are prone to pinching?
    Is it time to go tubeless?
    Any advice would help. Thx.
    Last edited by orangedotz; 06-10-2012 at 08:00 PM.

  2. #2
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    Has it always happened with these wheels and tires? Under what riding conditions? Front, rear, or both? How wide are the ignitors?

  3. #3
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    Quote Originally Posted by solomon707 View Post
    Has it always happened with these wheels and tires? Under what riding conditions? Front, rear, or both? How wide are the ignitors?
    Yes, just this set up (but I'm new). Mostly beginner singletrack with some advanced terrain. Both tires are pinching. 2.1 on both.

  4. #4
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    200# + narrow rims + low volume tires (2.1) = flats.
    Face it, you're a Clyde - go fat or plan on hike-a-bikes.
    Even on buff singletrack, it only takes one sharp rock, root, or a curb, and BOOM - you're toast.
    Check a Rampage, Ardent / Purgatory 2.4
    Learn to ride light and un-weight the wheels.
    Also, do not go too low, for me @ 210#, tubeless is 24/28 psi [w/tubes 30 / 35]

  5. #5
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    I disagree. Something else is wrong.

    I run a narrow DT TK7.1D which is less than 24mm wide with that tire. I have never had a problem. I would check your tires for sharp spots and also check your rim, as well as your rim tap to make sure everything is covered up.

    For the record, I am 250 without gear. I run 40psi in the front, and 45 in the rear.

  6. #6
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    Try higher tire pressure.
    Half our life is spent trying to find something to do with the time we have rushed through life trying to save

  7. #7
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    Are you sitting on technocal terrain?

    You should be standing and "riding light" over obstacles...

    SPP
    Rigid.

  8. #8
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    ^^ that and go tubeless.

    SPP
    Rigid.

  9. #9
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    The immediately solution to repeatedly pinching is more air pressure.

    Regardless if the pressure you're running works for other people, it doesn't work for you, your terrain, or your technique. Other solutions are riding lighter, higher volume tires, or tubeless.

  10. #10
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    what is causing the double pinch?

    i mean i have pinched a tube before and not known exactly what casued it but a double pinch is usually a pretty memorable experience since it usually requires a decent amount of rider error.

    if you describe a couple of these occurances i am sure we could help you better. at 40psi you gotta be doing something special to repeatedly make it happen...

  11. #11
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    I suspect what is happening is your spokes are puncturing your tubes. Make sure you check the rim tape. Sometimes it gets folded and that allows the spoke to pop up and touch the tube. Not much is needed to put a tiny tear in a tube.

    This used to happen to me all the time until I replace the rim tape on both rims and the problem is completely gone. I recommend the cloth-style tape (fondo?). It seems to work great.

  12. #12
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    [QUOTE=wjphillips;9398800 Make sure you check the rim tape.[/QUOTE]

    This.

    If you're running 40 psi, that should be good enough to eliminate pressure as a variable. Proper coverage of rim tape is the second thing I'd look for. Third would be bad tire installation technique.
    Last edited by HOV; 06-11-2012 at 12:31 PM.

  13. #13
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    Quote Originally Posted by wjphillips View Post
    I suspect what is happening is your spokes are puncturing your tubes. Make sure you check the rim tape.
    This? How? Only on an improperly tensioned wheel or a wheel that is hit so hard that the rim is bent enough to allow a spoke nipple to protrude. Rim tape is there to protect the tube from working it's way into the spoke hole and tearing, not to keep the nipple from poking through the tube. If this happens, one has more problems than just rim tape that has folded over.
    Sometimes, you need to go fast enough that the trail is a blur to find clarity. -- Wild Bill

  14. #14
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    I'm 135 pounds and when I rode with tubes I had to run my pressure at 45 psi and I still got flats.
    I know lots of guys your size and bigger who run Ignitors w/o a problem here in New England but they're all tubeless.

  15. #15
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    Quote Originally Posted by Malibu412 View Post
    This? How? Only on an improperly tensioned wheel or a wheel that is hit so hard that the rim is bent enough to allow a spoke nipple to protrude. Rim tape is there to protect the tube from working it's way into the spoke hole and tearing, not to keep the nipple from poking through the tube. If this happens, one has more problems than just rim tape that has folded over.
    You're right - I meant to only quote the part that said "check rim tape".

  16. #16
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    300 pounds riding on 2.0 tires at 45-50 psi. One flat in 3 years and that was a total sidewall tear out from snagging a small root. Otherwise, never flatted and I ride a lot of rocks and roots.
    Super snowflake = when an avatar offends you so much you have to cry about it and report it to admin. Life must suck for you.

  17. #17
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    How much air do you put into the tube before you mount it? You have to inflate it so the tube lose it's "flatness" and become round before fitting it. Too much air and the tube will be too long for the wheel and fold up in the end = remove the tube, deflate a bit and try again. Too little air and the tube is semi-flat and risk getting pinched when you put the tire on. So just enough air that you can no longer see where the tube used to be flat when deflated, but not so much that the tube gets too long and ends up folding.

    Once you have the tire back on, inflate the tube to a medium pressure, then pay attention to the tiny molding line on the tire, just a tiny bit above the edge of the rim. I'm not talking about the paint strip put on by a drunk factory worker, but the tiny line left over from the molding process. It should be just a hair above the edge of the rim all the way around, something like a tenth of an inch. If the distance between the rim and the molding line is bigger in one place, it might be the tire pinching the tube. Pay attention at the valve too, if the molding line doesn't sit right there, push the valve into the tire to allow the tire to get properly settled on the rim. If the molding line dives under the edge of the rim in some spots, just twist the tire to the opposite side with your hands to get the mold line to rise a bit. Once the mold line sits nice and even all the way around on both sides, inflate the tire to you normal riding pressure and check the mold lines a final time.

  18. #18
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    Quote Originally Posted by wjphillips View Post
    I suspect what is happening is your spokes are puncturing your tubes. Make sure you check the rim tape. Sometimes it gets folded and that allows the spoke to pop up and touch the tube. Not much is needed to put a tiny tear in a tube.

    This used to happen to me all the time until I replace the rim tape on both rims and the problem is completely gone. I recommend the cloth-style tape (fondo?). It seems to work great.
    That's not a pinch flat...

  19. #19
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    Quote Originally Posted by bad mechanic View Post
    That's not a pinch flat...
    You'll know if it's a pinch flat depending on where the tear/hole is.

    The issue with the spokes and the rim tape can happen on cheap rims. Like I said, it happened to me. I was running mavic X517 sups (rim brake) wheels. Once I replaced the rim tape, my flats went away (accept for thorns). I noticed that the tears/holes were on the inside of the tube. I would suspect a true pinch flat would tear the side of the tube, and thorn would tear the top/outside of the tube.

    I should also note that I had a lot of trouble with spokes on this wheelset (spokes breaking, coming lose, etc...) so perhaps my problem was unique. But I'd still replace the rim tape if I were you.
    Last edited by wjphillips; 06-11-2012 at 02:44 PM.

  20. #20
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    Quote Originally Posted by wjphillips View Post
    You'll know if it's a pinch flat depending on where the tear/hole is.

    The issue with the spokes and the rim tape can happen on cheap rims. Like I said, it happened to me. I was running mavic X517 sups (rim brake) wheels. Once I replaced the rim tape, my flats went away (accept for thorns). I noticed that the tears/holes were on the inside of the tube. I would suspect a true pinch flat would tear the side of the tube, and thorn would tear the top/outside of the tube.
    It's the tube working its way into spoke holes in the rim, not nipples backing out of the hole and puncturing the tube. If you had rim tape folding on you, then yes, the hole would be on the inside of the tube. Pinch flats are punctures out away from the inside center and are most often 2 holes, but sometimes one.
    Sometimes, you need to go fast enough that the trail is a blur to find clarity. -- Wild Bill

  21. #21
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    Quote Originally Posted by Malibu412 View Post
    It's the tube working its way into spoke holes in the rim, not nipples backing out of the hole and puncturing the tube. If you had rim tape folding on you, then yes, the hole would be on the inside of the tube. Pinch flats are punctures out away from the inside center and are most often 2 holes, but sometimes one.
    Yep. I think you're right.

  22. #22
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    Quote Originally Posted by bad mechanic View Post
    The immediately solution to repeatedly pinching is more air pressure.

    Regardless if the pressure you're running works for other people, it doesn't work for you, your terrain, or your technique. Other solutions are riding lighter, higher volume tires, or tubeless.
    Well said.

    And if money allows, you could add more suspension travel with a new fork and frame.

    One last possibility is that your rims have a sharp outer edge that. Although I would say this is a bit of a stretch.

    If it were me, I'd first try higher volume tires.

  23. #23
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    Are we sure they are pinch flats? Alot of people in this thread are talking about other kinds of flats. Try adding 5 psi and see if that solves the problems. Or you can change tires, something with a thicker side wall solved my problems of pinch flats. After that I went to tubless and that also solved the pinch flats.

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