Cog snapped!

leemolyneux
leemolyneux Posts: 24
in Road general
Coming Home yesterday up a stiff hill so was in my lower cog, in the standing position, a bit of traffic so I changed gear. I was nearly standstill before traffic started moving. As I started to move I applied abit of leg power then I heard a snap....... pictures will show the damage anyone explain just how!!??


L.Molyneux

Comments

  • pblakeney
    pblakeney Posts: 27,486
    Wow! Never seen anything like that.
    Possibly related, the manufacturers claim you can change under full load (standing going up hill is an extreme example) but it is not something I do as I've been cycling since before those claims were made. 😉
    The above may be fact, or fiction, I may be serious, I may be jesting.
    I am not sure. You have no chance.
    Veronese68 wrote:
    PB is the most sensible person on here.
  • leemolyneux
    leemolyneux Posts: 24
    It's horrendous. Im normally sitting to change but this time I decided I'll change whist standing!! Never again 😬
    L.Molyneux
  • Wheelspinner
    Wheelspinner Posts: 6,711
    I've seen a few reports of Shimano chainrings in the 105 and Ultegra series cracking like that. Not sure if it was ever identified as a batch casting issue or just random. Ask your LBS dealers - they may know, and may be a replacement program for them from Shimano?
    Open One+ BMC TE29 Seven 622SL On One Scandal Cervelo RS
  • leemolyneux
    leemolyneux Posts: 24
    Thanks wheelspinner definitely worth an ask, save me a good £120 too. 👍
    L.Molyneux
  • MattFalle
    MattFalle Posts: 11,644
    Price up junking the whole lot and buying a new crankset - most of the time cheaper than buying new 'rings plus you will get something where the face if it won't fall off as well.
    .
    The camera down the willy isn't anything like as bad as it sounds.
  • leemolyneux
    leemolyneux Posts: 24
    Will do definitely matt. No point buying new rings. I've had that crankset on for 2 years now but still shouldn't snap.
    L.Molyneux
  • Munsford0
    Munsford0 Posts: 680
    edited October 2021
    All the Shimano chainset fails I've ever seen involved the outer ring / crank moulding, never the inner. I'm wondering if you've lost a chainring bolt or two; you can see the vacant holes in the remains of the inner chainring. That might cause it to fold and snap like that in the circumstances you describe.

    Whatever the cause I'd agree with MF; a new chainset complete is likely to be cheaper than replacement rings, and it will give you peace of mind
  • MattFalle
    MattFalle Posts: 11,644
    Or go 1x..... pretty cheap option as well.
    .
    The camera down the willy isn't anything like as bad as it sounds.
  • masjer
    masjer Posts: 2,726
    Don't people repair things these days? A quick inspection for any damage- 1 minute. The large chainring looks ok. Replace inner chainring - 10 minutes.
    R7000 inner chainrings are only £20, and it'll functionally as good as new.
  • Munsford0
    Munsford0 Posts: 680
    That's also an option. £20 plus I'd suggest a new set of chainring bolts.

    As long as the failure hasn't ripped any of the original chainring bolts out of the back of the spider
  • hopkinb
    hopkinb Posts: 7,129
    I've ripped an inner ring before at the 50k point of a 100k out and back one February. Loose chainring bolt. Ruined the outer ring too, had to call for the support car, who wasn't happy...


  • masjer
    masjer Posts: 2,726
    Munsford0 said:

    That's also an option. £20 plus I'd suggest a new set of chainring bolts.

    As long as the failure hasn't ripped any of the original chainring bolts out of the back of the spider

    Yeah, definitely check the spider but if all's well it's a cheap fix. A two year old chainset isn't any age- is it still in warranty?
  • Dorset_Boy
    Dorset_Boy Posts: 7,610
    As others have said, inner chain rings are cheap. (Again the Fails spout their carp!)
    Just check the spider.
    It's the outers that are expensive and may as well be replaced by a whole new chainset.
  • MattFalle
    MattFalle Posts: 11,644
    Fuckme.

    Its an option, not a direction, all dependant how jeffed the whole crankset is which you can't tell from the piccie.

    Which is backed up by your second statement.

    Yet again DB shows his, well, we have no words. Its just z bit worrying.
    .
    The camera down the willy isn't anything like as bad as it sounds.
  • MattFalle
    MattFalle Posts: 11,644
    Please also notices "rins" plural in the post - inner and outer, plural and where the costs add up.

    reading, 101.
    .
    The camera down the willy isn't anything like as bad as it sounds.
  • Dorset_Boy
    Dorset_Boy Posts: 7,610
    MattFalle said:

    Fuckme.

    Its an option, not a direction, all dependant how jeffed the whole crankset is which you can't tell from the piccie.

    Which is backed up by your second statement.

    Yet again DB shows his, well, we have no words. Its just z bit worrying.

    Straight off you suggested inner chainrings are expensive to replace, which they are not.
    Bit like you stating the other day Swisstop BXP brake pads are really expensive compared to Shimano and others, which they're not because you thought they were sold in pairs, not fours.
    I suggest you check some actual facts before posting bad / incorrect advice.
  • First.Aspect
    First.Aspect Posts: 17,379
    Yes you shouldn't post bad advice.

    Personally I would try super glue first and see how it goes.
  • N0bodyOfTheGoat
    N0bodyOfTheGoat Posts: 6,065
    https://www.merlincycles.com/shimano-ultegra-6800-chainrings-74822.html works with 105 5800

    https://www.merlincycles.com/shimano-105-r7000-chainrings-153888.html has a slight tweak to the shape that doesn't naturally work with older 105 5800

    Full replacement 105 7000 crankset isn't cheap these days, like many Shimano components since Brexit/Covid
    ================
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  • masjer
    masjer Posts: 2,726
    N0bodyOfTheGoat said:



    Full replacement 105 7000 crankset isn't cheap these days, like many Shimano components since Brexit/Covid

    That's certainly true, the prices have escalated.
    I still prefer the older 5 arm cranksets with flat chainrings. All this 3d hollow shaped nonsense must account for some of the increased manufacturing cost.

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