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  1. #1
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    Crank arm falling off!!!

    Okay so I am still new to all of this but I have been getting better...

    I recently had to do some maintenance on my bottom bracket, which went well I might add, but now my crank arm on the left side of the bike keeps loosening. It actually loosened to the point that it fell off once! I re-tightened it, assuming I just didn't do it right the first time...but now it is loosening again...

    Why is it doing this and what can be done to stop it? Please help I don't want to ride it till it is fixed...

    Thanks for the help in advance!!!

    Also if anyone has any magic way of removing pedals that seem to be welded on cuz they are so tight that would be amazing too!!!
    Just a Kid chasing his Dreams

  2. #2
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    What cranks are they?

    Do you know which way to unscrew the pedals? One of them is reverse threaded....but I forget which one is. They can be a real pain in the ass to remove if they were put on too tight in the first place.

  3. #3
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    The crankset is Shimano TC-M361

    and

    I have no idea which way the pedals are supposed to unscrew...all I know is they are on there tight! The pedals are the Wellgo M-21 ATB. I have never taken them off since I got the bike 2 years ago... I have a set of pedals I want to switch them out for (got the other new set given to me) but couldn't get them off so gave up on the switch. I actually really like the Wellgos that are on it...they are cheap but feel great!
    Just a Kid chasing his Dreams

  4. #4
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    Bad news... You usually have to replace both the crank and the bb once an arm starts coming loose. The play wallows both parts. You might try locktite and over-torque it a bit, but budget some money for replacements. www. parktool.com/blog/repair-help/pedal-installation-and-removal-pw-3-pw-4-pw-5-hcw-16

  5. #5
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    Quote Originally Posted by rlouder View Post
    Bad news... You usually have to replace both the crank and the bb once an arm starts coming loose. The play wallows both parts.
    This was what I was expecting but hoping to not hear...

    What would cause the parts to begin to loosen in the first place? I torqued everything to the recommended specs when I reassembled everything, everything that was supposed to be greased was greased... what am I missing? I am very concerned about this because if/when I breakdown and buy new parts I want to be sure this doesn't happen again
    Just a Kid chasing his Dreams

  6. #6
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    Quick search for your crankset tells me that it uses the square taper bottom bracket. As rlouder indicated, once the interference becomes too loose, it's usually time for both a new crankarm and bottom bracket. However, if your crankset and bottom bracket are otherwise in good shape, you might consider cutting of a strip of aluminum off a beer/soda can and use it to increase the thickness of the square taper on 2 consecutive sides.

    As for the threads...left pedal and right bottom bracket (if English threaded) are reverse threaded (i.e. righty loosey and lefty tightly)
    Go on ahead, I'm gonna take a breather.

  7. #7
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    some loctite on the crankbolts too
    Rimmer - "There's an old human saying - if you talk garbage, expect pain"

  8. #8
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    Quote Originally Posted by winter View Post
    you might consider cutting of a strip of aluminum off a beer/soda can and use it to increase the thickness of the square taper on 2 consecutive sides.

    As for the threads...left pedal and right bottom bracket (if English threaded) are reverse threaded (i.e. righty loosey and lefty tightly)
    never would of though of this. Defiantly gonna give it a try!

    I think I got the bolts figured out, referring to which way to turn them...but still can't get them off.

    Quote Originally Posted by AlexRandall View Post
    some loctite on the crankbolts too
    Wouldn't loctite be deemed ineffective being there is the grease on the bolts? (Not shooting down your idea, I'm sure you know what you are talking about... just wondering for my own personal knowledge.)
    Just a Kid chasing his Dreams

  9. #9
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    I always remember the pedal direction by thinking that the right pedal has the 'right' or 'normal' 'righty-tighty, lefty-loosey' thread direction and the left pedal is 'wrong' (i.e. not the normal thread direction).

    The aluminum beer/soda fix sounds intriguing. I had this problem with an older Truvativ crankset. Torquing to spec or above spec didn't work and loctite didn't work. It seemed that it loosened faster every time I had to tighen the bolt. Smashing some metal into it (i.e. soda/beer can) is worth a try.

  10. #10
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    This might help some - i wrote on my pedal wrench "open: top + back" (translated from german). I dont care which way the thread works, i just pull the wrench to the rear to loosen the pedal.

  11. #11
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    I've got another mnemonic device for remembering how to get pedals off: forward on, back off. Meaning, you turn the wrench towards the back of the bike to get the pedals off.

    Also, this is the best pedal wrench I've ever owned. Tons of leverage, and canted at just the right angle. Technically, it belongs to my wife, as she had it before I met her, but it's in my tool box...and possession is 90% of the law.

  12. #12
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    when the cranks are on the bike, both pedals unscrew by turning them towards the back of the bike.
    Those are some old cranks,get with the new millinium or it maybe even just with the 90's, best vintage stuff was shimano octalink in xt.

  13. #13
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    So got the pedals off finally...decided that I knew for sure which way to turn them & they were coming off no matter what...whether they break and I have to drill them out or if they come off unbroken. I got them off but not before the wrench slipped off and hit me in the face....

    As far as the crank/BB problem I'm in the process of trying the "pop can idea" suggested by winter I'm going to ride it for a week or so and I'll update after I see if it works for me.

    Quote Originally Posted by herbn View Post
    Those are some old cranks,get with the new millinium or it maybe even just with the 90's, best vintage stuff was shimano octalink in xt.
    lol I know that I need to update them....the reason I haven't is I am working on (deciding on which I want) getting a new/my first full suspension 29er. This bike will turn into my beater bike...no need to upgrade just to beat the s**t out of it
    Just a Kid chasing his Dreams

  14. #14
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    Good job!

    Fixed and working great...

    So its been about two weeks...the crank that kept loosening hasn't loosen once since I put the pop can pieces in.

    I attempted to get 4 pieces around the BB but it was too tight so I ended up just using two on the sides I determined to be the most twisted/warped. If anyone is wondering I cut the can in the pieces about 3/4" long and 1/4" inch wide (didn't measure just guessed). I found placing a bit of grease on the back of the pieces (to hold them in place) then putting them inside the crank was the easiest way to getting it all together.

    Thanks for the help and ideas!!!

    Side note: Not sure if I would recommend this for a long term fix or not but so far it is holding up great and was a whole lot cheaper than replacing my BB and/or Cranks.
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    Just a Kid chasing his Dreams

  15. #15
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    Quote Originally Posted by moutainkiller View Post
    Fixed and working great...

    So its been about two weeks...the crank that kept loosening hasn't loosen once since I put the pop can pieces in.

    I attempted to get 4 pieces around the BB but it was too tight so I ended up just using two on the sides I determined to be the most twisted/warped. If anyone is wondering I cut the can in the pieces about 3/4" long and 1/4" inch wide (didn't measure just guessed). I found placing a bit of grease on the back of the pieces (to hold them in place) then putting them inside the crank was the easiest way to getting it all together.

    Thanks for the help and ideas!!!

    Side note: Not sure if I would recommend this for a long term fix or not but so far it is holding up great and was a whole lot cheaper than replacing my BB and/or Cranks.
    Thanks for reporting back on the fix. Glad to hear/read that this fix worked for you. Interesting that you placed the shims on opposite edges; I believe that putting the shims on 2 adjacent edges would create a more square profile (as opposed to a more rectangular profile when the shims are placed against opposite edges) to better fit the square taper of the bottom bracket spindle. Irregardless, glad it's working and may you have many more miles on this crankset.
    Go on ahead, I'm gonna take a breather.

  16. #16
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    Quote Originally Posted by winter View Post
    Interesting that you placed the shims on opposite edges; I believe that putting the shims on 2 adjacent edges would create a more square profile (as opposed to a more rectangular profile when the shims are placed against opposite edges) to better fit the square taper of the bottom bracket spindle. Irregardless, glad it's working and may you have many more miles on this crankset.
    Ya know it defiantly makes more sense using them on adjacent edges... might be tearing it down and changing the location of the popcan shims. If I do I'll post again on the level of success. Thanks again winter!
    Just a Kid chasing his Dreams

  17. #17
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    at a decent hardware store or tool supply you could get shim stock, all different thicknesses down to really thin, costs a bit more but not all that much.

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