Hello,

Shimano recommends not going lower than a ratio of 2, eg. 40T chainring and 20T cog so that the Nexus/Alfine hub doesn't get too much torque.

I read that a Nexus is meant to withstand a maximum torque of 50Nm, and even the 250W Bafang BBS01B mid-drive can add up to 80Nm to the mix.

Provided I pay super attention to never shift gears under load — stop pedaling, wait for the motor to stop, shift gear, resume —, could a Nexus 7/8 take the torque of a 40/23 combo (ratio of 1,73)?

And out of curiosity, what part(s) can break when applying too much input torque?

Thank you.