• Howdy! we're looking for donations to finish custom knowledgebase software for this forum. Please see our Funding drive thread

Ultra + Rohloff + belt drive & 60T/22T?


10 mW
Dec 3, 2019
Great Plains USA

I’m looking to build or buy-then-modify my second fat tire ebike. My first, which has been good, pairs a BBSHD with a 40T Lekkie chainring and Sunrace 11-46 cassette. Having biked with that arrangement for a couple of years now, I’d really like to move to an internal hub and belt drive so I can eliminate the derailleur, which tends to get damaged or clogged with grass/weeds with the kind of “backcountry”/off-trail biking I do (mostly on public lands where there are no trails).

A buy-then-modify option I'm looking at has a fat bike-sized Rohloff + Gates belt drive, and runs a 60T chainring and 22T (might be 26T) cog, powered by the Bafang Ultra M620 motor.

Does this sound like a reasonable/reliable combination for “backcountry” fat biking with a 275-300lb load (I’m usually hauling some photographic gear in addition to myself and the bike)? Or are there any concerns/downsides to this combination I should keep in mind?

‘Any thoughts/input appreciated!
A thought:

How much torque will it take with the gearing available to do what you want under your specific conditions? Can the IGH input handle that torque from the motor, and can the motor output that torque?

If your present system has the same torque and gearing and limits, and does what you want, then the new one should also do it.

I would recommend enclosing the belt drive / etc to keep things out of it to minimize maintenance.

If you get stuff in teh derailer, you're probably also getting it wrapped aorund the axles at the hub/gearing (if not now, you might with teh new system). Might consider some form of deflector to keep all that stuff out of any areas you don't want it in.
I originally thought the gear ratio might be too high but when I ran it through Sheldon Browns gear calculator, they look pretty similar.
As long as the Rohloff can take the torque .
That's a good idea amberwolf on the enclosure; I'll need to see if there is some kind of solution there.

I agree biphaeboh on the torque question, particularly in light of the 60/22-26 ring-cog combination. I did reach out to Rohloff to see if they had an opinion. I've come across some discussions about Rohloffs with different ring-cog combinations, but none of those were ebikes.