Originally Posted by
jonmanjiro
That makes sense. It would be interesting to know approximately by how much efficiency decreases / rate of wear increases as the cog size decreases. Do you know of any studies or research? It could be significant (or maybe not) in real world use.
Edit: I guess I'll find out for myself soon enough. I have a Bailout cassette winging its way to me as I type!
I definitely remember some a figure from some technical research paper. The pull force should drop like cosine of the angle between subsequent links. Links are always a bit loose, even on a new chain, so there is drop in force with which each subsequent link works. However, on small cogs, even with a new chain the cosine likely dominates. By Googling I found this paper: "Effects of Frictional Loss on Bicycle Chain Drive Efficiency", Spicer et al, J. Mech. Des. 123 (2001) 598,
https://doi.org/10.1115/1.1412848. They looked for frictional losses, that they tried to model, lubrication and stuff, but found that in measurements the cog size mattered most, with difference between 15T and 11T being consistently at the level of (1-3)% efficiency. This paper seems different from the one I remember from the past, but it is a start.