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The left crank kept falling off and I've kept on managing to put it back on but finally it wouldn't go. Think the threading is just absolutely kackered. So I ended up taking it to a shop to have a look at and a possible replacement crank. The only one advised to purchase was the Shimano FC-M622 175mm but it is near enough impossible to find and alot of places has discontinued the product. Does anyone know of any other cranks i could purchase instead of this one? Thanks, Tom.

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Do you need a 10 speed triple? Any more recent replacement of M622 shoud work (Hollowtech II bottom bracket). FC-M6000 should be absolutely fine. You just need to choose a double or a triple, just choose the appropriate variant (M6000-2 vs. M6000-3).

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If your rings are still in good condition, it's likely that you can replace just the left crank. https://www.sjscycles.co.uk/cranks-left/ Lists some that are available now. If you have (as your model number implies) a Hollowtech II crankset, any mountain crank using the same system will fit. As the main spindle is quite a hard steel, it doesn't usually get damaged from this type of problem. Remember, you can't look at both sides of the bike at the same time! (unless you use a mirror).

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  • Thankyou for the advice! Appreciated! – Tom Nugent Oct 18 at 15:42
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In addition, make sure you are installing the cranks correctly. Hollowtech 2 cranks are very robust and shouldn’t just spontaneously fall off.

  • Loosen and tighten the two pinch bolts in very small increments, 1/4 turn max at a time. Make sure to alternate sides.
  • It is imperative to use a torque wrench on these two bolts. If the tension is uneven, the crank won’t clamp on properly and is very liable to fall off. If you can’t access a torque wrench, tighten the bolts pretty much as hard as you can go with a regular length Allen key. If the threads strip out, your suspicion was correct: the threads were damaged.
  • Use threadlocker on the bolts.
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    I don't feel this is good advice. 'As hard as you can' could easily be 25Nm where the bolts are marked 14. I don't feel threadlock is a good idea either. If it's required, the crank must already be suspect. Using a torque wrench is good practice and avoids problems such as the original question. – JoeK Oct 17 at 19:17
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    @JoeK I’m assuming OP knows enough about wrenching to not be employing gorilla strength while doing it, and they were most likely not doing it tight enough previously. A little over tightening probably isn’t a big issue when the alternative is a new crank anyways. The threadlock just serves as a bit of peace of mind; medium strength won’t permanently freeze the bolt in place or anything. – MaplePanda Oct 17 at 20:28
  • Thankyou for the advice! – Tom Nugent Oct 18 at 15:43
  • Would the FC-M610 fit to the hollowtech II? – Tom Nugent Oct 18 at 16:09
  • You are very welcome. I don’t know enough about the different models to be able to guarantee compatibility, unfortunately. The splined interface is the same on all MTB cranks, but the outwards splay of the crankarms might be different. – MaplePanda Oct 18 at 18:43

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