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  1. #1
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    xtr crank sheering

    I posted this on the Drivetrain board but figured I may get more hits over here. yes this is on my superfly.

    Shimano FC-M970

    Finally getting back on the bike after a long winter. Purchased this crank last March so it is only a year old. I have 300 plus miles on it. Went for a 30 mile on road ride and at mile 28 noticed my right foot getting wobbly. got home and noticed the entire inside of the crank where the pedal goes in was sheered. First what would cause this, second is there anything I can do to fix this, and third would this be a warranty issue? The left pedal is in perfect and no issues. I rode 2 24 hour races with this set up. I have no idea what would have caused this. I can almost slide the pedal into the slot now with out screwing it on to the crank arm.

  2. #2
    himom!
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    So the threads are screwed up? Maybe a helicoil could fix it?

  3. #3
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    Cross threaded?

  4. #4
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    My guess would be a loose pedal moving around stripping the threads, but I have never seen that happen. I have seen pedals coming loose, but it hasn't stripped the threads. Pictures would be helpful. If it was caused by a loose pedal then it probably won't be covered by warranty.

  5. #5
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    Quote Originally Posted by Fishlips
    My guess would be a loose pedal moving around stripping the threads, but I have never seen that happen. I have seen pedals coming loose, but it hasn't stripped the threads. Pictures would be helpful. If it was caused by a loose pedal then it probably won't be covered by warranty.

    I will have to get pictures when I get home. Not like this is going to matter but I was using shimano pedals also. parts of the inside are smooth from the sheering, so the pedal will not really take at all. Oh and the threads on the pedal still look perfect! I really do not know what went wrong!

  6. #6
    no fat chicks
    Reputation: iliketoridebikes's Avatar
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    dude are you serious
    your pedal came loose, its not that hard to figure out
    usually happens on junky cranks but i guess your luck sucks
    your fault no warranty
    #1 NORBA elite singlespeed racer 30-34 age group

  7. #7
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    I guess you should know who put the pedals on. If it was the shop, you need to bring this to their attn. If it was you or a buddy, SOL.

  8. #8
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    I can guarantee you the pedal is not on backwards, this is why I am so confused.

  9. #9
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    Quote Originally Posted by mtnbkr33
    I can guarantee you the pedal is not on backwards, this is why I am so confused.
    I don't think anyone is saying the pedals were put on backwards. Rather, they either loosened up or were cross-threaded when installed initially. As for the threads on the pedal still being in good shape, I think generally the pedal axle is going to be a harder metal than the crank, so the crank threads are going to be the ones that suffer the majority of the damage when cross threaded. A good shop may be able to save the crank by re-threading it.

  10. #10
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    Quote Originally Posted by Fishlips
    I don't think anyone is saying the pedals were put on backwards. Rather, they either loosened up or were cross-threaded when installed initially. As for the threads on the pedal still being in good shape, I think generally the pedal axle is going to be a harder metal than the crank, so the crank threads are going to be the ones that suffer the majority of the damage when cross threaded. A good shop may be able to save the crank by re-threading it.
    Ahh my bad. I was kind of replying to the above post about who put the pedals on and whatnot. I guess I am just frustrated and can not figure out how this could happen.

    Excuse my ignorance but can you cross thread even if you put the pedals on correctly?

  11. #11
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    No worries. I am sure some shop guys can answer better, but I think you can do it if you the pedal axle is not going in straight and you just keep cranking away. If it is difficult at all to thread the pedal then you are crossing threads. You can do the same thing with bottom bracket.

    So are there no threads on the inside of the crank? Or is just the threads nearest to the outside?

  12. #12
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    When pedals come out of cranks, it is usually because they are not tight enough to begin with. I did not say they were in backwards. That is not really possible. I'm just saying they were loose. Spending all day riding, allowed the pedal to work it's way out of the crank until it pulled the last couple of threads out at the end. I've seen this many times before.

    A good shop can do a heli-coil in there, and save the crank, or tap it out from the inside out, and save it that way too. There should be plenty of threads left in the crank for that.

    I hope this all works out for you.

  13. #13
    You know, for kids
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    Quote Originally Posted by 202cycle
    I did not say they were in backwards. That is not really possible.
    I've seen it before, it most definitely is possible. Gave up on trying to separate the arm from the pedal and wound up replacing both.
    disclaimer: I sell and repair bicycles

  14. #14
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    Quote Originally Posted by madcap
    I've seen it before, it most definitely is possible. Gave up on trying to separate the arm from the pedal and wound up replacing both.
    A friend of mine did this with some nice sugino cranks I gave him. What a waste of nice cranks.

  15. #15
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    had this happen on a Look road crank, I didn't tighten

    the pedal into the crank tight enough so it was loosening as I rode and finally came out. The thread on the pedal was fine but the threads inside the crank arm were stripped out. I took it to the LBS who chased the thread (actually like rethreading) with a tap and was able to rethread the pedal back in the arm. That was a year ago and it still is tight and works fine. Good luck, I know I felt pretty bad when the pedal fell off.

  16. #16
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    I had this happen on a FireX crank. SRAM was nice and warrantied it. They replaced my 1.1 FireX 175mm cranks with 1.1 Stylo 180mm. I don't know how Shimano is about warranty stuff, but try. Since it is XTR they might be fine with it. Going through your LBS helps too.

  17. #17
    SSolo
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    Loose pedal and/or a really hard pedal strike can seriously damage these threads....continuing to ride on it well....the aluminum cranks will lose to the steel or titanium pedal spindle.

    And yes, you really can put the left-handed thread into the right-handed crank if you put a wrench on it. Never seen it, but I've seen some seriously whacked assembly
    Fat, drunk, and stupid is no way to go through life son...

  18. #18
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    Overtorquing of the pedals is waaaay overlooked. You overtorque a pedal enough then put someone on it for 30 miles and boom, most of the pedal threads are gone. If your initial threads are all that are damaged, your pedal came loose and then ripped out as it loosened. If most (60-90%) of your threads are damaged or gone, the pedals were over torqued and your weight combined with your power output caused the threads of your cranks to fail. The pedal spindles are made of super hard steel and will win the fight over super hard aluminum any day of the week.

    That being said, you would really have to over torque the pedals as XTR cranks are pretty strong. I bet that it just came loose and then ripped out.

  19. #19
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    Thanks for all your replys! I looked at it a little more last night. I would say 2/3rds of the threads are sheared off. So that leaves me with 1/3 of the inside threads (inside meaning nearest the frame) am I just asking for trouble if I put my pedals back on with locktight? I am buy no means bashing Shimano. This is absolutely user error. I am going to say that I under tightened the pedals as I was in a hurry to get a ride in.

  20. #20
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    Quote Originally Posted by mtnbkr33
    Thanks for all your replys! I looked at it a little more last night. I would say 2/3rds of the threads are sheared off. So that leaves me with 1/3 of the inside threads (inside meaning nearest the frame) am I just asking for trouble if I put my pedals back on with locktight? I am buy no means bashing Shimano. This is absolutely user error. I am going to say that I under tightened the pedals as I was in a hurry to get a ride in.

    Step 1 is the have the crank re-tapped from inside out. If you can't get a good enough threading of the pedal on that then step 2 will be a helicoil.

    I would not try to thread them on now without re-tapping those threads

    G
    You can't depend on honest answers from dependant hands...

  21. #21
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    Ditto G-Live's comment. Go to a bike shop with a good mechanic and get it fixed right and hopefully salvage your $400 cranks. It should be a pretty quick and cheap repair.

  22. #22
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    Quote Originally Posted by Fishlips
    Ditto G-Live's comment. Go to a bike shop with a good mechanic and get it fixed right and hopefully salvage your $400 cranks. It should be a pretty quick and cheap repair.
    Ditto (tritto?) that. I bet you will have to get them helicoiled, but that's not a bad thing...

  23. #23
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    You could just go buy a tap and try to save the current threads. That will probably work. If it does not work then you have lost nothing except the small cost of the tap.

    After that just get an insert.

  24. #24
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    Thanks guys! Called the LBS and he is going to try an retread the crank arm. if that does not work i will try the helicoil. anyone know what size I will need if it comes down to that?

  25. #25
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    Not to bash bike shops but I bet other places like a machine shop would be a much better place to get a helicoil. Or even a gunsmith does that much more than a bike shop.

    also if the bike shop is gonna charge you a ton just to run a tap through it, know that a tap in the correct size is not that expensive.

    http://www.use-enco.com/CGI/INSRIT?P...PARTPG=INLMK32

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