Snapped chain

Thomson0
Thomson0 Posts: 49
edited December 2012 in Workshop
I changed the chain on my winter bike around 200 miles ago and it snapped on Sunday right in the middle of a set of traffic lights, which didn't half make me look stupid!

It was a dura ace chain which when I tried to work out what had happened looks as if the outer plates are worn at both the leading and trailing edges, the inner plates don't appear to have any wear on them. I have checked the front and rear derailours and there isn't any sign of rubbing and the cassette appears to be in good condition, the large chainring has some wear but not a massive amount.

Does anyone have any suggestions why this might have happened?

Thomson0

Comments

  • alfablue
    alfablue Posts: 8,497
    I think Dura Ace chains are directional, implying that one side differs from the other; what you see as wear may be the design. See here.

    Does the wear look like this?
    4496_da7901.jpg
  • I never thought of that Alfablue yes the wear does look like that, the link that had snapped had gone on the leading edge and appeared to have snapped rather than worn completely through.
  • alfablue
    alfablue Posts: 8,497
    Was it fitted the right way round? (see the Shimano Tech document)
  • I think it was but I will check in the morning and get back to you thanks for the suggestions btw.
  • keef66
    keef66 Posts: 13,123
    You won't have induced any wear in 200 miles; the side plates are shaped to improve shifting and reduce noise. How did you shorten / join the chain? Did you use a Shimano joining pin or a quick link eg KMC Missing Link? Did the break occur at the joined link?
  • I've abandoned the Shimano 'directional' chains, as I've had two dura-ace 7901 chains snap and both showed several cracked outer plates. I just think they are too fragile. Stick with KMC L or SL and quick links.
  • I've had a chance to check the chain now and it was on the correct way, looking at it closer it isn't showing any signs of wear but it has broken clean though on both sides at the leading edge pin on one of the links. The chain was shortened with a park tools workshop chain tool and I used the correct shimano joining pin.

    I will say in the chains defence that it probably wasn't design with the idea of 15 stone of finely honed flab stamping on the crank arms to get away quickly from the car revving its engine behind me at the lights. The fact that it has broken both plates at the same place makes me a bit wary to keep using the chain cos I still have the section of chain that I cut to reduce the length and I could splice it back in.

    I think I will have a look around at some of the other brands of chain and get a stronger one for the rest of the winter.
  • alfablue
    alfablue Posts: 8,497
    Go for a KMC
  • Had a quick look at KMC I am not sure which would be the best for the job any suggestions?
  • alfablue
    alfablue Posts: 8,497
    They are all good, Pay more and they get lighter and gold but the saving of 50g can cost a lot. Try Merlin cycles for good deals. Never had a breakage with KMC. I spend about £20 per chain
  • Thanks for the info.
  • You should send it/ take it back to Shimano and see what they say. A breakage after 200 miles would indicate a manufacturing fault 15 stone or not. They are designed for the likes of Mark Cavendish to sprint on and he generates an awful lot of power.
  • Was it being used on a triple chainset? None of the 'directional' chains, including Ultegra are supposed to be used with a triple. Something to do with the lateral flexing of the chain, although it's very difficult to find the information and it doesn't appear on any of the packaging. Madison, the UK importers won't replace a snapped directional chain under warranty if it's been on a triple. Just don't tell them.
  • andrew_s
    andrew_s Posts: 2,511
    Derek48 wrote:
    I've abandoned the Shimano 'directional' chains, as I've had two dura-ace 7901 chains snap and both showed several cracked outer plates. I just think they are too fragile. Stick with KMC L or SL and quick links.
    That's a manufacturing defect.
    The pins on 9/10/11 chains are peened at the ends to make them grip the outer side plates when the pin doesn't project right through, and sometimes the heat treatment/hardening of the side plates leaves them too brittle and they crack.
    I've heard tell of it happening on other brands too, but less often.
    http://forum.ctc.org.uk/viewtopic.php?f ... 58#p182005
    http://www.bikeforums.net/archive/index ... 90043.html
    viewtopic.php?f=40042&t=12873546#p17816521
  • The chain was on an ultegra double chainset I took the broken links into my LBS yesterday and the mechanic said that the chain wasn't worn and it had snapped both plates at the same link which is something he has seen many times before. The shop don't even sell shimano chains any more so I bought a SRAM chain which probably cost me a few pounds more than the net but the advice and confirmation that the rest of the groupset wasn't damage was worth it.
  • sturmey
    sturmey Posts: 964
    Not ALL Dura Ace chains are directional. Misleading to suggest this. Only the latest 7901 are directional afaik.
    Dura Ace 9 speed chains aren't. These are a robust chain and silent running. Raced on them without any issues.
  • The latest Dura Ace 9000, 11speed chains are not directional. If directional chains are so good why would Shimano revert to a non-directional chain unless there had been some problems????!
  • Pigtail
    Pigtail Posts: 424
    I had a pretty new 9 speed kmc chain snap last year. The night before the Etape Caledonia. Fortunately the bike shop in Pitlochry was still open and sold me a new SRAM one as they didn't have KMC. One side plate had snapped and two others were cracked.

    It has really put me off KMC, but I've seen reviews claiming the same thing with SRAM!
  • alfablue
    alfablue Posts: 8,497
    I think all the brands have the potential for failure; and if a shim breaks on you for example, it puts you off. That said, in 29 years of MTB, continental tours and road riding in uk, I seem to favour KMC based on my experience, though there is zero science involved!
  • Chris James
    Chris James Posts: 1,040
    alfablue wrote:
    They are all good, Pay more and they get lighter and gold but the saving of 50g can cost a lot. Try Merlin cycles for good deals. Never had a breakage with KMC. I spend about £20 per chain

    Maybe I have been unlucky, but I have had two breakages.

    I still like them though.
  • nathancom
    nathancom Posts: 1,567
    Thomson0 wrote:
    The chain was on an ultegra double chainset I took the broken links into my LBS yesterday and the mechanic said that the chain wasn't worn and it had snapped both plates at the same link which is something he has seen many times before. The shop don't even sell shimano chains any more so I bought a SRAM chain which probably cost me a few pounds more than the net but the advice and confirmation that the rest of the groupset wasn't damage was worth it.
    I run a SRAM chain on my winter bike and it has been very good and a decent price. I think you will be happy and you don't need any special tools to change it when the time comes.