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About 4 weeks ago I installed a new SRAM PC-971 chain on my Surly LHT. This morning I've noticed that one of the outer chain link plates started to pull away (to spread in a way that the pin is not engaged with the outer plate). My previous chain had failed in exactly the same way, but it was 50% worn according to a chain stretch checker. While riding this bike on a daily basis for over 6 years, I've never had this happen before. Does anyone have any ideas of why the chain is repeatedly failing in this fashion?

Drivetrain details:

  • RD: Deore XT
  • FD: Tiagra, triple;
  • Cassette: SRAM 9-speed, 11-32t (reasonably worn, but not skipping yet);
  • chainrings: original to the bike, reasonably worn, the teeth don't look terrible yet.
  • What do you mean by "pull away"? A photo would help. – ojs May 31 '16 at 17:52
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    I would check for a bent tooth somewhere in your drivetrain, under shifting a wayward tooth could bend the chain outer link plate away. – Rider_X May 31 '16 at 18:04
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    Did you close the chain when installing it by using a quick link or partially pressing a rivet out then pressing it back in? – Batman May 31 '16 at 18:37
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    I closed the chain using the supplied gold master link. By "pulling away" I meant that the chain link had spread so that one side of the outer plate was no longer engaged with its pin. – ilya May 31 '16 at 21:00
  • Rider_X, thanks! Your theory sounds very plausible and certainly fits the symptoms. – ilya May 31 '16 at 21:06
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You might not be installing the pin correctly. It sounds as if you did not reach the seating point or past it. Here is an article on Shimano chain installation (See drawings). http://www.parktool.com/blog/repair-help/chain-installation-derailleur-bikes

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    Because Park like the shuffle their website regularly, invalidating all links, it's much better to summarise the article and provide the title rather than just a link. We have a lot of broken links to Park from here, unfortunately. – Móż Jul 16 '16 at 2:34
  • What pin? This SRAM PC-971 chain almost certainly came with a master link. Unless he didn't know what that is and didn't use it ... – Kaz Jul 16 '16 at 23:43
  • Comment from May 31 from OP under question: I closed the chain using the supplied gold master link. – Kaz Jul 16 '16 at 23:45

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