new 9-speed chain fails after 4 weeks and ~240 miles 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.
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