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Replacement Octalink crank arm

TheBigBeanTheBigBean Posts: 17,156
edited March 2012 in Workshop
My left crank arm broke into two peices last night and I'm struggling to find a replacement. It is a Shimano 105 FC 5501 / 5504 and 175mm in length. Is it possible to replace it with any left 175 that fits a v1 Octalink spline, or do I need exactly the same model? On Sheldon Brown's website, it lists a number of other models that fit this spline such as the Ultegra 6500 - this model seems to be availble for £60 or so (a little steep). Also, would the ISIS version work and what do I need to search for to get this?

If I can't find a replacement, does anyone have any recommendations of what I should do. I like my bike and don't wish to retire it, but also a complete new 105 crank set seems excessive. Is it worth it, or is there a cheaper option?

Many thanks for any adivce that can be offered.


  • schweizschweiz Posts: 1,644
    I have a set of Ultegra 6503 Cranks, 172.5mm, chain rings have been replace and done +/- 10,000 km so plenty of life left (52/42/30).

    I'm sure we could come to some arrangement if you want them.
  • YossieYossie Posts: 2,600
    If you don't mind it looking different then yes, any 175mm Octalink compatible crank arm will work.
  • TheBigBeanTheBigBean Posts: 17,156
    schweiz - Thanks for the kind offer, but as yours are 172.5 I would need to change both sides and I only have a double chain ring, so I think this would end up being expensive and beyond my mechanical skills.

    Yossie - Thanks. I don't care in the slighest how it looks, so if I can find one then that is a solution.
  • YossieYossie Posts: 2,600
    No worries

    I have a set of FSA compact cranks available (wiil double check which exact model) - I'm not sure whether they are 172.5 or 175: doubles, they've done 50 miles so as new, £50 inc p & p if you are interested?
  • keef66keef66 Posts: 13,123
    Would you really notice a 2.5mm discrepancy between cranks?
  • YossieYossie Posts: 2,600
    Undoubtedly not, but if a) you don't want to and b) you don't have to, why do it?

    TBB isn't after 1981 Campy Unobtainable so he has to make do until something turns up - he just wants a boring Octalink 175mm crank arm, that's all. I can't really blame him for wanting matching length 'arms.
  • TheBigBeanTheBigBean Posts: 17,156
    Thanks for the replies. I had not really considered the possibility of a different length - I'm far from the experienced mechanic and assumed it wouldn't work. I mean, why make them in 2.5mm increments if no one can tell the difference?

    Anyway, as Yossie says, I expected to be able to find a replacement part like for like without needing to buy a different length and an unrequired chain ring. I used to ride old school Dawes bikes from the 80s and earlier and it appears easier to buy parts for them than a relatively modern Cannondale. Still, I have come to realise that it's not easy to get a 175mm left Octalink crank arm, so I guess I'm going to have to compromise.

    Options, I have found so far:
    1. 170mm 6500 from Only £10, new, but 5mm short. Will I notice that?
    2. 172.5mm 5501 on ebay. Includes both crank arms and chain rings. Used. £57.
    3. 175mm 6500 from various. Left only. New. Around £65.
    4. Those listed above, although I don't know much about the FSA ones. I can't seem to buy those new either.

    I'm quite tempted by the £10 quick fix, but is 5mm a lot of a difference? Option 3 would seem most sensible, but also seems like throwing money at an unsupported system.
  • John.TJohn.T Posts: 3,698
    Octalink is now a redundant system and has been for some time. Parts are like rocking horse manure.%mm is quite a lot of difference. Don't forget it is 10mm on the full circle.
    Only Shimano made octalink so you can not fit any other make to that BB. Your best option is to get a complete new crank set and BB or at least a current standard used one.
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