moxfyre

I'm currently reading "Bicycling Science", and there's some research in it showing that the efficiency of a 53/15 drivetrain is about 93%, less than a 53/20 drivetrain, about 96%. I can find the exact figures and references if anyone's interested. This is including a rear derailer and non-straight chainline. The principle is that the chain has to bend more around smaller sprockets, causing greater frictional losses.

All the mechanical research in the book fascinates me, it's a really good read.