Originally Posted by
fietsbob
Mountain drive (mine) is a Reduction gear (130-54) the Speed drive 110 is an overdrive 34-'54',
but the frame BB edges must be Chamfered That is where the torque transfer is..
It's no longer the case for the SpeedDrive sold under license by ATS from Taiwan:
Welcome to ATS
https://bikegang.ecwid.com/#!/Brompt...ATS/p/60194073
In terms of price, a SpeedDrive comes between a front derailleur and a Alfine/Rohloff built by Kinetics.