11sp derailleur or hub gear? Either way, if it is a BB-motor, plan ahead for gear changes or your gears will be fairly short-lived.
There's an argument for Di2 integrated with the ebike system on this basis, as the motor knows when to back off.
Its quite tricky because front and rear are not locked together. I think this is standard on etandems with motor on the front. The front can freewheel independant to the rear, so we can get out of sync.
Mostly this happens over the top of a rise I'll ease off and my wife just keeps pedalling. (
) Even easing for a change seems to be enough to put you little out of sync. Mostly this doesnt matter but it can start to feel pretty lumpy on steep climbs where we are both pushing hard. We are still very much learning, my wife is an experienced stoker but not an experienced solo rider - she took my lead through feel in the pedals as to how much effort to push.
But on the strength of 2 runs, the motor is making a huge difference to how I feel at the end of a run. My knees are not shot, but we still get a work out. Its much closer to a solo effort for me.
I feel less need to conserve momentum over bad surfaces/through corners, so in that respect I think its probably safer, but it doesn't handle as nicely as our bob jackson orbit.
And it still rolls into the berlingo, wheels on and everything. So far so good.
