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A place to ask bicycle repair questions, and for bike shop monkeys to share advanced non commercial wrenching resources (no YouTube self promotion). This is only for repair related topics.

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What would cause a master link/missing link to break? (lemmy.ca)

submitted 9 months ago by [email protected] to c/[email protected]

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I had my first dropped chain... as in, the chain fell completely off my bike. The side of one pin on the KMC missing link appeared to have popped right off. Nothing else was missing or damaged.

That link was the original and had only been removed once since the chain was installed, approx 900km before, when the cassette was replaced around 800km ago.

The only recent change to my bike was buying new wheels, but other than reindexing (at the LBS), shifting was excellent before and after the wheel swap.

Was it just bad luck, or is there something that might have caused this that I should watch out for?

The replacement link says reusable (Original KMC), but perhaps the original with the chain isn't as strong?

I'll note that this happened on a very casual ride, so no added weight, hills, or power going through the pedals. I shifted and it fell off. 😵

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[–] [email protected] 1 points 9 months ago* (last edited 9 months ago)

This is a random guess: if the chain fell off while shifting, then the sideways forces of the derailleur acting upon the replaceable link could have dislodged the pins. But if the link was secured on both its faces, this shouldn't be possible. So instead, it could have been that one link face wasn't secured, and by sheer luck, the replaceable link never happened to 1) be at the derailleur while 2) shifting gear ratios.