Backpedaling-how important it is for an ebike?

jeffpetersen

10 mW
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Jul 24, 2013
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I and my friend are working on a setup that converts a bike into ebike, but currently there is slight resistance on cassette-enough to prevent any backpedaling. So I was wondering how important backpedaling is for a pedal assist ebike?
 
I have no answers, only a couple questions:

First, does this mean the cranks also can't stay still while the wheel rotates? I assume so, since that would require the very same freewheel action that back-pedaling requires. So you'd have to pedal along with the wheels, like a fixed gear bicycle.

Second, how could it do that? I don't know anything about cassettes, but I assume they have the same internal pawl spring freewheel mechanism, and it seems to me something must be gravely boogered to make that fail.
 
Sorry. Gotta ask...

I'm aware of folks riding w/assist doing "faux pedaling"... but to pedal backwards? Explain please?
 
So imagine you touch the cassette very lightly with finger. Enough to create some amount of friction.
Now, if you try to backpedal, the top portion of the chain (between chainring and cassette) will have no tension due to the friction. I hope this explains a bit more...
 
"Now, if you try to backpedal"... Point being? (Sorry. again...)
 
Usually if thats happening, the frame is very lightly touching the freewheel and needs to get spacered out a little more.

The circle marks are from a freewheel rubbing.
 

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To answer your question, there should be no more issue "back pedaling" an e-bike than any other bike. If there is an issue, you need to fix it. E.g. chain dragging somewhere, something going on with the freewheel unit, etc.
 
Nailed it!

Should be no friction whether rubbing on frame and needs spacers (I used a washer from Home Depot) or the thingy's inside the freewheel/cassette, gosh whats the name of those thingy's that click.
 
markz said:
Nailed it!

Should be no friction whether rubbing on frame and needs spacers (I used a washer from Home Depot) or the thingy's inside the freewheel/cassette, gosh whats the name of those thingy's that click.

Pawls.
 
I'd guess he's driving (or sensing the tension of) the top of the chainline, and the device he's doing it with is causing this problem.

Since he won't say or show us, we can't help him fix it, though.
 
Sounds like you might need to clean and regrease the freehub’s bearings. Or you can just spray wd40 on it (this works temporarily, but it’s not a good idea because it actually destroys the grease).
 
Just an fyi since it got brought up... theres a big difference in behavior depending on if the freewheel is rubbing the frame, and whether its internally seized up. The second one is the dangerous one, as when the freewheel is rubbing the frame, it still stops when coasting, even though you cant backpedal. When its internally seized, it tried to keep spinning with the wheel and pushing chain ahead of it when you stop pedaling, leading to some serious and possibly dangerous derailment of the chain.
 
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