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Chain dropping under load.

ElushionElushion Posts: 115
edited February 2014 in Workshop
Bit of a weird one, looking advice.

Was racing today and noticed that the chain is dropping of the big ring to the inside (small ring) under load.
However, it moves up and down on the small and big chainrings perfect, it also seats perfect.
I can put it in the 11 and really drive it and nothing happens, but if I have it between say 21-25 tooth and put some load on it, it drops from the big ring to the small.

The front derailleur is set fine, and the teeth on the chainring as in good condition. Got a new chain put on it there recently, but be damned if I can see what the issue is.

Any ideas?
"It was eleven more than necessary."

-Jacques Anquetil (after winning a race by twelve


  • At a guess I would say that you are using a 53 outer ring with the 2nd to last or last rear sprocket (i.e. the lowest 2 gears 21 or 25 tooth) and as such you are cross chaining. I have seen it often and I remain puzzled why people do it so often. The angle that the chain sits when attempting to maintain what is an acute chain angle ( between outer ring and 2nd to bottom gear) means there is a risk of it slipping off. Is it an 11 speed - although cassette width may not be a factor if you were to observe the position/line of the chain in these combinations I bet it isn't poker straight.

    So cross chaining - maybe that's the problem.

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