• Also that second chainring just chillin'...

    It's a ghost ring, sometimes seen on the timing chain of a tandem instead of the more common eccentric front BB, also on singlespeed conversions with vertical dropouts where there is no magic gear solution.

  • Does it hurt efficiency or decrease chain life?

    Efficiency should be slightly better than using a sprung tensioner with a jockey wheel, as the ghost ring has exactly zero bearing losses and the chain roller and side plate friction would be about the same.

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