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Thread: POS Cranks

  1. #1
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    POS Cranks

    Well my generic shimano oem cranks are being a real b-tch. At first the left crank would come loose every two rides or something, now ive got 10 minutes before it comes out, and ive lost 2 dustcaps. this is on a trek 4500 XC mtb. Any help on how to fix this or if i have to get a new crank ( ) would be great

    Thanks

  2. #2
    Just give'er. hooligan's Avatar
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    Cheapness is not the solution. Save for a new crank?

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    Are you torquing the bolts down tightly enough? I have a 4600 and have never had this problem, even when I had my low budget 820.

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    the bolts are torqued almost to the point where it slows the rotation down, im not sure whats wrong. this started happening after i took my bike in somewhere cheap (it was the only place i could bike to with the bb in that condition) to get it serviced, it happend about a month or two after and it wont stay tight, i dont know what to do.

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    Use a torque wrench, get it right to the point where it needs to be(manufacturer specs). I think that it should be almost impossible to turn, not just to where it slows down, but anywho, go with a calibrated torque wrench and manufacturer spec, and there should be no problem.

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    well one time i got it really tight, but there was friction somewhere and the bb rotation was slowing down. a friend sugested something might be slightly stripped, any thoughts?

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    The Rabbi seely's Avatar
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    Ok what you did was strip out the taper. If the crank arms are going down far enough that the arm is rubbing the bottom bracket, there are two possibilities, both of which sound likely at this point:

    1) you stripped the square hole on the crank arm (if its loose and you ride with it, it doesn't take long... also will occur if you over tq the arm)

    2) if the BB is loose it may have backed out enough that your crank arm is getting close to rubbing it (hence the slowed rotation when you tighten the arm down)

    What you will need is a new crankset and a torque wrench to fix the problem. And don't grease the spindles when you install the new arms.

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    some of that made sense to me...long story short, could it be blamed on the idiot who serviced my bike?

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    I think seely nailed it. And, most likely the "chump" who serviced the bike isn't at fault.

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    ok thanks, youve been a big help. well i was down taking a look at my bike, the actual crank arm isint rubbing against the frame. i also managed to get my front derailer from sort of out of whak to useless. this bike is almost more trouble than its worth.

    on an unrelated note, if anyone would like to buy a slightly used boutique bike with 'trek' and 'alivio' stickers all over it to prevent theft, contact me

  11. #11
    mmm babaghanouj. rasheed's Avatar
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    hey my.ark.4, were you the one who was riding the don with some friends a month or so ago and asked me if i had an allen key because your cranks were loose right by the water filtration plant?

    current ride: 2003 norco vps fluid 3.0 (custom build).



  12. #12
    Senior Member GreenFix's Avatar
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    You can try some blue loctite on the tapers and the crank arm bolt threads too. If you have rounded the taper at all on the crank arm (I am assumin it is a square taper), it will come loose again quickly. Chalk this up as another argument for splined cranks.

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    the cranks are splined, ive seen that when servicing the bb, do you think locktite will just be a quick fix, or can i get by on a season or so with it. and to rasheed, no, that wasnt me, but ive really wanted to go there, those masive sets of stairs, and the north shore flower planters everywhere...mmmmm

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    The Rabbi seely's Avatar
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    Quote Originally Posted by my.ark.4
    the cranks are splined, ive seen that when servicing the bb, do you think locktite will just be a quick fix, or can i get by on a season or so with it. and to rasheed, no, that wasnt me, but ive really wanted to go there, those masive sets of stairs, and the north shore flower planters everywhere...mmmmm
    If they are the "cheap Shimanos" they aren't splined. You won't get anything splined on a Shimano until you go Deore level. I used to build A LOT of 4500's and unless there were big changes for 2004/5 there is no way they are splined!

    And locktite is also just a quick fix, and you are using the bike way outside of what it was meant for, so just suck it up and buy some cranks (preferably a new bike) that was meant for what you are doing.

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    Custom User Title: jallen's Avatar
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    This exact same thing happened to me on my at-the-time NEW hardrock '04 sport.. like the second time I took it off road, my left crankarm fell off when I was 4 miles away from home, not long after a little jump I did.

    I didnt have tools with me, so I looked really silly pedaling one legged most of the way home, and walking up big hills. I had a pair of powerpedal straps, thank goodness for that, it would be impossible to pedal at all without that, or clipless'.

    My LBS put it back together for me (it was under warranty), and I havent had problems since.

    Really really sucked when it happened.

    Sorry Seely, from your other posts you dont need more ammo about specialized.. hehe

    -Tim

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    The Rabbi seely's Avatar
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    Eh actually I ride a Specialized... but if you want to talk about crank arms falling off check out the low end Treks and Gary Fishers. It got to the point that we would remove the bolts and locktite and retorque just as an extra step in assembly with any bike with those Suntour cranks.

    Quote Originally Posted by jallen
    Sorry Seely, from your other posts you dont need more ammo about specialized.. hehe

    -Tim

  17. #17
    NCAA - DUAL CHAMPIONS! a2psyklnut's Avatar
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    Quote Originally Posted by seely
    Eh actually I ride a Specialized... but if you want to talk about crank arms falling off check out the low end Treks and Gary Fishers. It got to the point that we would remove the bolts and locktite and retorque just as an extra step in assembly with any bike with those Suntour cranks.
    We used to do the same with all the Gary Fisher's in the shop! I guess Trek doesn't know what proper "torque" means.
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  18. #18
    Custom User Title: jallen's Avatar
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    Quote Originally Posted by seely
    Eh actually I ride a Specialized...
    Sheez! I am sorry, I got you mixed up with another forum regular.. I am sorry! Maybe I got you mixed up cause you LIKED specialized as opposed to someone who was on the warpath about them..

    Sorry about that..

  19. #19
    Humaniod Typhoon -Stretch-'s Avatar
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    on my hardrock, the mech at the shop torqued the balls outta my cranks when i took it to get my wheel trued...said they werent tight enouf if he could move the bolts...
    04 specialized hardrock xc with eggbeater sl pedals
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  20. #20
    The Rabbi seely's Avatar
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    Quote Originally Posted by jallen
    Sheez! I am sorry, I got you mixed up with another forum regular.. I am sorry! Maybe I got you mixed up cause you LIKED specialized as opposed to someone who was on the warpath about them..

    Sorry about that..
    Actually that was me that posted the Specialized rant. I USED to like them (2004 and prior) but 2005 I feel like they've gone straight down the crapper, faster than I could have imagined. That being said I still love my Stumphumper!

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