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  1. #1
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    Catastrophic failures of thorn resistant QTubes

    Pardon the double-post here: I posted in the General forum first, not realizing that the tube geeks probably hang out in the Wheels and Tires forum instead, but all the answers I got there relate to trying different tube solutions--and right now I am specifically trying to address the Kenda QTube failure issue before I call them about it. Original thread here: Thorn Resistant QTubes breaking, but here was my question:

    With nine of us all mountain biking and racing (yes, I have a wife and seven mountain-biking children), I am tired of changing blackberry-thorn- and goathead-induced flats on my regular Kenda QTubes and thought back to the time a few years back when I put in a super-thick tube that lasted about three years until the stem finally broke off (although I cannot recall the manufacturer now).

    I understand many of you will recommend that I simply go tubeless, and that may happen some day, but I just don't have the time to convert all 12 or 13 of our mountain bikes--everyone has one, plus two shared single-speeds and a loaner or two. That would be somewhere around 25 rims to replace or adapt for tubeless, to say nothing of changing the fluid periodically.

    Despite tubeless being a great idea for a solo, pair, or even a trio, the thought of all that work is more than a bit daunting for me, so I resume the real story, where I happily trotted off to my favorite bicycle supply shop and purchased a pair of QTubes thorn resistant tubes for each of us--for just about twice the prices of a regular tube.

    Double the price for five times the life seemed like a good idea at the time. In reality, though, in the last six weeks, two 29er tubes have split down the inside seam, and my 85-pound 13-year-old-son has had the valve stems break out of two 26" tubes. None of these failures was associated with a jump, hard turn, any particularly intense braking, or other tube trauma.

    The bike shop is perfectly willing to warranty these for us; however, I do not know if I want to continue replacing these if they continue to fail. My 13-year-old is afraid to have these tubes in his tires for his 100-mile MTB race in two weeks. He would rather risk the pinprick of a thorn hole than a catastrophically broken tube. Of course, we can pre-slime the tubes or use thorn-blocking strips, and probably will, but it still leaves this question:

    Is it just us, or has anyone else had issues with these particular Kenda QTubes? It seems to me that four catastrophic failures within six weeks indicates either a bad batch (not likely, given that there are both 26 & 29 involved here), poor design, poor quality control, something we are doing incorrectly (other than riding every day), or maybe just bad weight/pressure combinations. The QTubes on my bicycle have not yet failed, but then I weight about 185, so I could surmise that they a problem only with lighter riders. Possible? Ideas?
    Last edited by Brain; 07-09-2013 at 11:52 PM. Reason: Rewording

  2. #2
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    It sounds like your tube problems are related to poor quality. If I were in your shoes, I would switch brands (Slime offers some nice tubes made by CST). BUT, your son deserves a nice tubeless setup for his 100 mile race, in my humble opinion. Not only do thick sealant-filled tubes add weight, but they also add rolling resistance. Give him every advantage you can!
    Tire Design & Development Engineer. The opinions expressed in this forum are solely my own.

  3. #3
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    If the chance of flatting is greater than average in the areas you ride, I would look into something like these for your son's 26" wheel bike:

    Specialized Bicycle Components

    And go ahead and go tubeless.

  4. #4
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    Not really higher than average chance of flats--just more bodies in this family than most. This hundred-mile race is only one of many, many rides and races this year (520 individual races last year for this family), and I have spent well over $50,000 on cycling stuff in the past four years--just something I accept as the cost of having seven bicycle-riding/racing children, but it still gives me pause when I consider upgrading everyone to tubeless or tough tires. We have tried some tough tires in the past, and the problem has been that they are so stiff that it is all but impossible for little hands (and even mine) to get on and off the rim--which is why we have several hanging on the wall in our carport.

    I did end up getting some detailed replies to my other post--related to stiffness of thick tubes making them slip inside the tire and ripping off the valve when braking. I am apparently not the first to experience this as a systemic issue.

    I have pretty much decided to go back to our regular-weight tubes with Stan's inside. That sounds like a good middle-ground approach for now.

    Thank you!

  5. #5
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    If the whole family is having trouble with tubes, that would be a lot of work as well.

    If you get a hole in a Stans filled tube, it may hold air for that ride, but in my own experience trying that route, it will still need a patch after that ride, and if you think dealing with a straight up tubeless setup could get messy, adding a tube that has leaked can be even more so. If you get a hole in a tubeless setup, you just let the sealant plug the hole, and the overwhelming majority of the time, it's a done deal.

    Seems worth a shot to try it with one and see how it goes.

    Since this topic gets beaten to death here regularly, I won't evangelize 'tubeless vs. tubes' any further, just saying that I have done the Stans in the tube thing and found it wasn't for me.

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