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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 1 year ago by [email protected] to c/bikewrench

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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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[–] PlantJam 2 points 1 year ago

My best guess is that the chain wasn't installed correctly to begin with. Exactly how is anyone's guess. It's possible to miss half of the connection on some brands of quick links, though. The chain would look pretty close to normal unless you were really looking for that issue.

[–] [email protected] 2 points 1 year ago

I snapped a new one trying to pop it into the locked position before. Now I just align the pieces together and on the upper of the loop it and step on the pedal while breaking. Other than that I've never had them break or fall apart if they were opened and closed less than 8 times even if they are non-reusable.

Opening them is just cursed though. I need a tool with like 1 meter arms

[–] [email protected] 1 points 1 year ago* (last edited 1 year 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.