Originally Posted by HappyHumber
My biggest suspicion is that I might have let the chain slack.
That would be my guess too. A slack chan can wiggle so that the top of a tooth bumps into a side plate. That can generate a LOT of force on a fixed gear.
Originally Posted by
Gordiep
I don't know if it's of any significance, but the OP was running an odd-number cog on an even chainring. Jedi Master Sheldon contraindicates this, as it contributes to uneven chain wear (if I understand him correctly, which isn't certain). 48/17 is a pretty beefy ratio, especially with a 230lb guy mashing down suddenly-- could uneven chain wear combined with such a monster load have caused the cahin to fail?
Not clear that it's a "monster load." Indeed, it doesn't sound like it to me. The magnitude of the load is related to the size of the sprocket driving the chain, not the ratio.
Thus, the pedaling load is _less_ with a large ring like a 48 than it would be with, say, a 42.
If the force was being applied by the rear spocket, as when resisting to slow down, a 17 tooth sprocket would not pull as hard a a smaller one, say a 15, would.
Sheldon "Loose Chains Break" Brown