I'm looking at the third one down and wondering: why aren't all-wheel-drive bikes a thing? (Well, steering...) I guess there is such a thing: http://christinibicycles.com/ – sounds pretty complicated: 'A handlebar-mounted switch controls the AWD “shift on the fly” clutch. When the clutch is engaged, the rear spiral gear interlocks with the rear hub and power is transferred via internal shafts to the forward spiral ge…
And why in the first place, there is no benefit.