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  1. #1
    ramjet
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    i won’t do this justice but here goes:

    so i'm flyin' down this hill yesterday and out of nowhere my back wheel locks up. no, i was not braking. mentally, i've decided that a wreck is imminent and i brace for impact. it never comes. i just keep skidding like i used to as a kid on my bmx bike with a pedal brake. i eventually come to a stop and jump out of the saddle in time to see the tube which has been pinched off by the carnage pictured below, expand and blow. kaboom! fortunately i was just a couple miles from home and as i hoisted my steed onto my back a good-sam in a pickup stopped to give me a lift.

    the guys at the lbs were shocked and amazed. the rim is only 3 months old so they are saying factory defect. so, i got a new wheel and tube for free. the dear wife picked up the bike today and brought it by the office so i'll be making my 12 mile ride home within the hour.

    only concern now is where the tire locked up and skidded along the asphalt, the tread is exceedingly worn there. looks like new tires for christmas!

    best,
    rmg

  2. #2
    more ape than man timmhaan's Avatar
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    holy crap! that's crazy.

  3. #3
    370H-SSV-0773H linux_author's Avatar
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    - model rim please?

  4. #4
    ramjet
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    Bontrager Camino

  5. #5
    Senior Member mechBgon's Avatar
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    I see the side wall of the rim blew right off the rest of it. That would release the bead of the tire, and the tire would then expand sideways from the pressure in the tube. That's probably what caused the wheel to stop rotating... the tire no longer fit through the space between the chainstays or seatstays anymore.

    Unless there was a rock stuck in your brake pad that had cut a groove into that side of your rim to weaken it so it broke like that, I would tend to think "factory defect" too.

  6. #6
    Mad bike riding scientist cyccommute's Avatar
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    Quote Originally Posted by mechBgon
    I see the side wall of the rim blew right off the rest of it. That would release the bead of the tire, and the tire would then expand sideways from the pressure in the tube. That's probably what caused the wheel to stop rotating... the tire no longer fit through the space between the chainstays or seatstays anymore.

    Unless there was a rock stuck in your brake pad that had cut a groove into that side of your rim to weaken it so it broke like that, I would tend to think "factory defect" too.
    Because the strip of metal seems to be uniform and above the "joint" between the inner wall of the rim and the brake surface, I'd suspect a stress riser from a rock or piece of debri in the brake pads rather then a defect.

    What was the pressure on the tire, Zonatic?
    Stuart Black
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  7. #7
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    Good ridin' cowboy. Pretty amazing how you can skid a rear wheel and stay up. I was in a bike race once where a guy ahead of me crashed into the rear wheel of a guy next to him. The impact didn't knock him off the bike, but bent the rim so much it locked against the chain-stays. He just stayed on his bike for what seemed forever, straight as an arrow till he skidded to a stop and then just fell over! It was in the days of toe clips and straps and he couldn't get his foot out.

  8. #8
    JRA...
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    Quote Originally Posted by cyccommute
    Because the strip of metal seems to be uniform and above the "joint" between the inner wall of the rim and the brake surface, I'd suspect a stress riser from a rock or piece of debri in the brake pads rather then a defect.

    What was the pressure on the tire, Zonatic?
    that was my first thought, but then many new rims have "wear indicators," which is basically a groove in the rim sidewall, which could easily cause such a incident if machined too deeply.

  9. #9
    Banned.
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    It's relatively easy to keep a bicycle upright when the rear wheel locks up, just keep steering a straight course until you come to a stop. Locking up the front wheel almost always ends in a crash.

    Locking the rear wheel becomes very dangerous on a motorcycle, if it occurs at speed, and if you release the rear brake before the motorcycle has come to a stop. Releasing the rear brake will allow the wheel to regain traction, and cause the motorcycle to kick up, throwing the rider off. This is know as "highside" crash and can be fatal.

  10. #10
    ramjet
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    Quote Originally Posted by cyccommute
    Because the strip of metal seems to be uniform and above the "joint" between the inner wall of the rim and the brake surface, I'd suspect a stress riser from a rock or piece of debri in the brake pads rather then a defect.

    What was the pressure on the tire, Zonatic?
    65 lbs. (max)...and there was a lot of loose gravel along the stretch i was riding...hmmmm.
    thanks,
    zonatic

  11. #11
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    check out this rim - lbs was stunned
    See how dangerous reflectors are?

  12. #12
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    check out this rim - lbs was stunned
    It was the reflector, I'm sure of it!!

  13. #13
    Mad bike riding scientist cyccommute's Avatar
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    Quote Originally Posted by dafydd
    that was my first thought, but then many new rims have "wear indicators," which is basically a groove in the rim sidewall, which could easily cause such a incident if machined too deeply.
    D'oh. I'd forgotten about this bit of stupidity from some rim manufacturers. Mavic puts just a little machined divot in one spot but I have read about the wear indicators going around the entire rim. Now it makes sense. The wear indicator groove would make a natural weak spot which could easily fail.

    Now I agree with the shop. Zonatic, make sure they don't give you a wheel with these stupid indicators on them. I've built dozens of wheels and never found wearing through the rim to be that much of a problem. They usually fail from some other mode rather then wear through.
    Stuart Black
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  14. #14
    Mad bike riding scientist cyccommute's Avatar
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    Quote Originally Posted by zonatic
    65 lbs. (max)...and there was a lot of loose gravel along the stretch i was riding...hmmmm.
    thanks,
    zonatic
    See my above post. I'm assuming that this was a mountain bike tire. 65 lbs isn't that high although for a wide tire, there is more lateral stress than a road bike tire but I've pumped wide mountain bike tires higher without problems.
    Stuart Black
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  15. #15
    Czar of Dirt
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    Trek/Bontrager may be interested in knowing about that rim failure. Be sure the shop or you let them know the deal....

  16. #16
    totally louche Bekologist's Avatar
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    I've seen some rims at the LBS with what looked like WAY TOO DEEP wear indicator grooves.They were probably Bontrager's (Treks' Wallyworld bike supplier) Did I miss something, or is no indicator, or a pinhole indicator, not good enough anymore?

  17. #17
    Bike Junkie roccobike's Avatar
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    Quote Originally Posted by Czar of Dirt
    Trek/Bontrager may be interested in knowing about that rim failure. Be sure the shop or you let them know the deal....
    Zonatic, glad to hear you are OK. Actually, Czar of Dirt has a very good point. Trek and Bontrager must keep records of complaints and if a trend develops, a recall would have to be initiated. Additionally, I don't see why you should pay for the replacement tire. Your LBS should have gone to bat for you and contacted TREK, I'll bet they would give you a new tire free, in return for getting their hands on that rim IMHO.
    Roccobike BF Official Thread Terminator

  18. #18
    Senior Member duckliondog's Avatar
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    Too bad nobody was behind you too watch the rim peel apart. I wouldn't know what to do if I saw that happening to someone.

  19. #19
    One Tough Cookie. Black Bud's Avatar
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    Yikes! Looks like someone took a potato peeler to the thing!

    I'm not surprised you stayed upright, though; a rear skid can be easily recovered from, if you are a good rider...and that must describe you! A front wheel skid, however, is a different story...did the shop check both rims, just to make sure there is no problem with the front one? Might be worth it.
    A bad day on the bike is better than a good day at work!!

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