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  1. #1
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    LX Cranks Thread weakness?

    I was running a outboard bearing LX crank on my single speed.I went over a 1 foot drop.I felt the pedal come loose.When I stopped, I find that the pedal had taken the threads out.Do the LX cranks have this weakness in the threads?I'm 240 and have not had this happen before?I noticed that the new SLX has a pedal insert.I have 3 rides on my now junk crank set. The pedal was in straight and tight-no cross thread.

  2. #2
    Hmmmmm
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    That's weird, my LX crank has two metal inserts in each crank arm.
    I've ridden on mine, since 04. My cranks have been on two different bikes and have untold thousands of miles on them. I lost track after about 5K.
    I finally had to replace the BB about 6 months ago and have had several chainrings on them.
    Two big rings, 3 or 4 middle rings and three grannys.
    I tighten the none drive side pinch bolts progressively and just snug up the preload cap on the end.
    I used to weigh about 215 and now weigh 190lbs.
    I have rode them entirely at Bootleg Canyon.
    Bottom line; mine have been legendary and others around here, have survived being on downhill sleds in the hands of pros and semi pros.

    Later, Eric.
    "I thought of that while riding my bike."
    Albert Einstein, on the theory of relativity.

    Peace and Long Rides...

  3. #3
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    Similar experience

    I had a very lightly used set develop the same issue (drive side arm) where the pedal stripped out the thread. They were installed tightly too...I am ~220 and was using them on a single speed. This set had no steel inserts (580 series IIRC).

  4. #4
    Hmmmmm
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    Quote Originally Posted by CJLED
    I had a very lightly used set develop the same issue (drive side arm) where the pedal stripped out the thread. They were installed tightly too...I am ~220 and was using them on a single speed. This set had no steel inserts (580 series IIRC).
    Are you sure you don't have inserts?
    They aren't threaded in. The inserts are pressed into two slots on the end of the crank arms.
    "I thought of that while riding my bike."
    Albert Einstein, on the theory of relativity.

    Peace and Long Rides...

  5. #5
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    mine did not have inserts.The threads were in the crank arm.itself.

  6. #6
    Hmmmmm
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    Quote Originally Posted by 29erPilot
    mine did not have inserts.The threads were in the crank arm.itself.
    Look at the end of your crank arm, like you're looking from the end towards the spindle. You should see two grooves. Those grooves are where the steel inserts are pressed in. The LX M-580 doesn't use a threaded steel insert, they use two thin steel plates, pressed in 90 deg to the pedal axle, from the very end of the crank arm.
    They press the inserts in, then machine the pedal threads.
    I like it that way, because they won't accidentally unscrew, like standard inserts occasionally do. It does make them hard to spot though.
    "I thought of that while riding my bike."
    Albert Einstein, on the theory of relativity.

    Peace and Long Rides...

  7. #7
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    mine is a m582.We have inspected it and have found no steel plates.The threads are all aluminum.We can scratch into all of the threads with a file .It's just soft aluminum.We chased all the threads on the good side and no steel.I have a couple of engineers looking it over and they both come to the same conclusion.

  8. #8
    Hmmmmm
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    Quote Originally Posted by 29erPilot
    mine is a m582.We have inspected it and have found no steel plates.The threads are all aluminum.We can scratch into all of the threads with a file .It's just soft aluminum.We chased all the threads on the good side and no steel.I have a couple of engineers looking it over and they both come to the same conclusion.
    Ok...you got me to do a closer inspection of my M-580 cranks, and indeed there are no steel inserts.

    To explain myself: When I had bought them about 4 years ago, the tech info that I had read, said they had steel inserts.
    I vaguely remember talking to someone, that had explained that they had steel plate type inserts, pressed into the end. I had cranks before like that and there are two "grooves" in the end of my crank arms, so I assumed all this time, that the inserts are there.

    The only explanation I have for the durability, is that my Shimano Pedals thread all the way through, using all the threads in the crank arms.
    I also use automotive anti seize and I just snug them up.
    I don't know about the pedals you guys are using, but I have seen lightweight XC pedals, that don't thread all the way through crank arms.
    That could be a potential weakness.
    I wasn't kidding, about the miles I have on mine or the fact that I've seen LX M-580s survive downhill use.....Hmmmmm.
    I wonder if they had a bad batch go out?

    Eric.
    "I thought of that while riding my bike."
    Albert Einstein, on the theory of relativity.

    Peace and Long Rides...

  9. #9
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    i hit a rock with my pedal on my 08 lx cranks and it ripped the threads out...pedal seems to be fine. i was going decently fast and wiped out pretty good though, so it probably could have happened to other cranks too. i only weigh 185

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