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I've recently had the LBS replace the freewheel on my eBike after 500 ish miles of riding. The sprockets were not worn out, instead the freewheel bearing (not the hub bearing) had become loose. It looked like this was due to the bearing cup loosening on it's thread. My attempts to tighten it were futile, the LBS appeared unwilling to even attempt to do so, rather assuming that it was due to a low quality part.

They also claimed that it might be because it was not an eBike specific freewheel. Does such a thing even exist? If it does, what about an eBike makes such a thing necessary?

I challenged the LBS on that claim. They say the freewheel sees additional load. For a mid drive eBike that might make sense, but for a hub drive I don't see how that's possible.

  • " Does such a thing even exist?" Their existence is strongly implied by what the shop said to you. If you think they're so skeevy that they'd pretend that fake products exist, you should find another bike shop. But look at it this way: what do you think they'd have done if you said, "OK. I guess I need an e-bike-specific freehub. Please order me one." Because, really, the only possible answers are "Certainly, sir, it'll be here on Monday" and "Oh, er, I just made that up and they don't actually exist." Which do you think is more likely? – David Richerby Nov 30 '18 at 12:07
  • @DavidRicherby Other options include: They do not deal much/at all with eBikes equipped with freewheels. They merely inferred the existence of eBike specific freewheels from the existance of eBike specific cassettes. The particular mechanic seemed to be baffeled by the concept of a freewheel, so that is certainly a possibility. – maxf130 Nov 30 '18 at 12:31
  • In that case, the shop seems to be completely incompetent and you should go somewhere else before they break your bike! – David Richerby Nov 30 '18 at 13:35
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    @DavidRicherby That is the impression I got. In any case I don't let them near our bikes. I brought them just the wheel. – maxf130 Nov 30 '18 at 14:01
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    In this day an age, a new bike with a freewheel (clicky bit inside the cogs) is a sign of an average to low-end bike build down to a price. I'd expect other parts to be similarly short-lifed. – Criggie Dec 1 '18 at 1:58
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Given that this question has failed to attract an answer, I will speculate a little.

The (probably) false reasons

The only text I could find online regarding Freewheels and eBikes is as follows:

Most of our rear hub motors have a threaded side cover which takes a standard screw-on freewheel gear cluster, rather than the more modern cassette freehub system. While you can purchase freewheels from most bicycle stores, they are rarely available in more than 7 speeds and even then almost never with an 11 tooth small gear, which is essential to maintain a decent pedal cadence on fast ebike systems.

This implies that there is nothing mechanically special about freewheels sold for eBikes. They do however have unusuall many speeds (whether or not that is wise is probably another question) and a large ish range.

The large range is useful because it means you can do without a front derailleur.

Mind you, none of the above is special to eBikes. Road and mountain bikes also benefit from being able to go fast, and go up steep hills.

The (I think) real reason

Freewheels with 8 or 9 speeds are essentially useless on most bikes since they tend to lead to bent and broken axles. Therefore freewheels with more than 7 speeds are restricted to rear hubs with unusually robust axles.

Rear hub motors for eBikes typically seem to have slightly larger diameter axles. The axles on my bike is about 12mm. This is necessary to pass out the electrical connection through the hollow axle. This means it is possible to mount a freewheel with more speeds with less risk of bending or breaking axles.

It's worth mentioning again that the above is more speculation than anything else.

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I agree with you that a hub drive e-bike should not impose any more stress on a freewheel than a conventional bike. Whichever wheel you drive, the torque supplied by the motor is not going through the freewheel. The torque transmitted by the freewheel is all generated by you, just as on a conventional bike. A stretch would be to claim that you can generate lots of torque in short intervals, then let the motor drive you in between, while on a conventional bike you would have to be working all the time so the torque peaks would be lower.

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