Originally Posted by
nwmtnbkr
Safety is the biggest issue. Hub motors cannot be placed on aluminum or suspension forks because they have cast drop outs that fail without notice (due to the affects of torque), causing loss of control and serious injury. Torque arms won't help stop such failures.
That one's been bugging me since the day I started looking into eBikes and realized that they transfer the torque by that little spline thingie against the dropout slot itself.
Seems like a fatal design flaw to me. I've got Rohloff hubs on two of my bikes and they do it right: no spline, but a torque arm connected to the chain stay. I weigh over 200# and have hammered those two bikes pretty hard with no hint of failure.
I'm no engineer, but it seems like eBIke hubs sb set up to use dual torque arms and not load up the dropout's slot.
Awhile after posting what's above, I stumbled on what seemed at first (to my uneducated eye) tb a pretty good discussion of the tradeoffs:
http://tinyurl.com/y9vjjbo
But a quick read indicates it says nothing... nada... zip... zilch.....bupkis about the obvious safety issue around fork integrity.