How easy to damage IGH?

For discussions about bikes and equipment.
gregoryoftours
Posts: 799
Joined: 22 May 2011, 7:14pm

How easy to damage IGH?

Postby gregoryoftours » 27 May 2018, 10:50am

How easy is it to damage internal hub gear mechanisms by shifting under load and/or with badly adjusted cable tension? I'm specifically talking about Alfine 8 when fitted on mid-drive e-bikes, so substantial assisted torque can be going through the gear mechanism. These bikes are used by people who are often not familiar with how to shift well or correctly, so may shift gears under full pedaling load.

Brucey
Posts: 30785
Joined: 4 Jan 2012, 6:25pm

Re: How easy to damage IGH?

Postby Brucey » 27 May 2018, 11:50am

the Nexus 8 and (low normal) Alfine 8 hubs are specifically designed to upshift under load without great trauma, under modest load. Downshifts are another matter; the same kind of shift servo as is used in high normal A8 and A11 for upshifts (and discussed at some length in recent weeks in the A11 thread) is used in these hubs (but for downshifts) too. I think this does leave the hub vulnerable to damage under loaded shifting. Like you say a sensible rider might back off the pedals but a non-integrated motor system won't.

IIRC shimano Steps is integrated in such a way as the motor backs off during shifting but other types of mid-motor are not, and the result is a potentially graunchy shift. Even Steps can give a bad shift 5-4 on Nexus 8 hubs, I think.

BTW it is kind of moot as to whether the shifting is the main problem with these drives or not; it isn't at all unusual for the IGH to simply wear out within the warranty period, e.g. on heavily used carrier type e-bikes. The reason for this is that instead of 150W pedalling you might get 250W motor plus 150W pedalling on these machines and they might be doing a lot more miles too, e.g. in the hands of a commercial courier or something.

Front motor e-bike drives and drives that power the left side of the rear hub do not load up the transmission (in fact quite the reverse) and thus have an advantage there, even it they are not perfect in other respects.

cheers
-------------------------------------------------------------------------------
~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~