Bent crank, sprocket or crankshaft??

machinebike
machinebike Posts: 39
edited September 2016 in MTB general
I have a downhill bike with a single sprocket that is wobbling and rubbing the chain guide and I tried bending the little tabs that the sprocket mounts to and made a slight difference but still has a noticable wobble.

Can a bike shop correct this or is it inevitable to buy a new crank set?

Comments

  • cooldad
    cooldad Posts: 32,599
    Who knows. Is the spider bent, the chainring? Is the BB trashed?
    I don't do smileys.

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  • The Rookie
    The Rookie Posts: 27,812
    What crankset?

    Very unlikely the axle is bent, much more likely its either just a bent chainwheel or spider.

    Remove chainwheel and use a screwdriver or cable tie to the back of the mounting tabs by holding it to the frame and so check if the mounting tabs are running true, if they are its the chainwheel!
    Currently riding a Whyte T130C, X0 drivetrain, Magura Trail brakes converted to mixed wheel size (homebuilt wheels) with 140mm Fox 34 Rhythm and RP23 suspension. 12.2Kg.
  • JGTR
    JGTR Posts: 1,404
    You will need a new crank arm now that you have bent the mounts, hopefully it is that crank arm that was bent in the first place and not something else.
  • machinebike
    machinebike Posts: 39
    I took off the sprocket and bashguard, mounted the pedal arm and measured distance between the 4 tabs and the chaingguide plate. 2 of the tabs were slightly off. Maybe off just enough for the sprocket to throw a serious wobble?

    I have a Holzfeller crank
  • Monty Dog
    Monty Dog Posts: 20,614
    You may be able to bend the spider tabs a bit - use a big, adjustable spanner to ease them into position. Bend it too much and they'll crack/break.
    Make mine an Italian, with Campagnolo on the side..
  • rockmonkeysc
    rockmonkeysc Posts: 14,774
    Holzfeller cranks have quite a weak spider. I've bent one and I've seen a couple others bent. You'll be lucky to get it properly straight.
    Transition Patrol - viewtopic.php?f=10017&t=13070235
  • machinebike
    machinebike Posts: 39
    RockmonkeySC wrote:
    Holzfeller cranks have quite a weak spider. I've bent one and I've seen a couple others bent. You'll be lucky to get it properly straight.
    Yeah thats crazy considering the cost of these cranks.
  • machinebike
    machinebike Posts: 39
    Monty Dog wrote:
    You may be able to bend the spider tabs a bit - use a big, adjustable spanner to ease them into position. Bend it too much and they'll crack/break.
    Im not familar with an adjustable spanner....Ill google it.
  • rockmonkeysc
    rockmonkeysc Posts: 14,774
    machinebike wrote:
    RockmonkeySC wrote:
    Holzfeller cranks have quite a weak spider. I've bent one and I've seen a couple others bent. You'll be lucky to get it properly straight.
    Yeah thats crazy considering the cost of these cranks.

    As cranks go they're pretty cheap.
    Transition Patrol - viewtopic.php?f=10017&t=13070235

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