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[cargo bike] Replacing gear hub with derailleur?

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[cargo bike] Replacing gear hub with derailleur?

Old 06-23-23, 12:47 AM
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[cargo bike] Replacing gear hub with derailleur?

Hello,

For use in a hilly terrain, that Bafang BBS01B-powered cargo bike needs smaller ratios, way lower than the max chainring/cog ratio of 2 recommended by Shimano — eg. a 40T chairing combined with a 23T cog = 1,73.

In case the Nexus 7 can't handle it even while paying attention never to shift under load with the motor on… what about replacing the transmission with a derailleur instead?

Can that frame take a derailleur?

Thank you.

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Old 06-23-23, 01:08 AM
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What kind of cargo bike is that? Things look awfully ... normal. Short answer is, no that frame won't take a derailleur. Back in the day, derailleurs came with their own hangers and were mounted on the axle. If you could find something like that. Sturmey-Archer IGH hubs are pretty tough. I'm no IGH expert but there must be one around that can take the heat if the power is used responsibly. Cassettes aren't without their failures in e-assist use cases. The ones rated for that kind of abuse are hellishly expensive and normal ones don't last anywhere close to a normal lifespan.
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Old 06-23-23, 01:28 AM
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Thanks

It's a Bakfiets.

SA stopped making their eight-speed hub, and a three-speed wouldn't be enough

Rohloff is way too expensive

It doesn't look good :-/

--
Edit: Looks like a Nexus 8 could do the trick. With a 40T chainring and a 20T cog, and thus a ratio of 2, the smallest speed gives 2,14m/26,8"

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Old 06-23-23, 03:20 AM
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Originally Posted by Winfried
Hello,

For use in a hilly terrain, that Bafang BBS01B-powered cargo bike needs smaller ratios, way lower than the max chainring/cog ratio of 2 recommended by Shimano — eg. a 40T chairing combined with a 23T cog = 1,73.

In case the Nexus 7 can't handle it even while paying attention never to shift under load with the motor on… what about replacing the transmission with a derailleur instead?

Can that frame take a derailleur?

Thank you.

I have nothing useful to add, but where did you get that golden color locking tab for the axle? I've been looking for something like that forever.
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Old 06-23-23, 07:32 AM
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The LBS installed it.

Non-rotation washers depend on the angle of the dropouts.

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Old 06-23-23, 07:41 AM
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What about just changing the front ring to be smaller. That will give you lower ratios to allow for climbing more easily. Whether derailleur gear's or internal gear's, you still will need to slack off on the power somewhat when you shift.
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Old 06-23-23, 11:24 AM
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It's been done, but still too big. The concern is over-torquing the Nexus 7.

In case that 40/23 + BBS01 combination kills it, I'll try a Nexus 8 with a more reasonable 40/20.

Thank you.
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