Do you need a freewheel if you have a geared hub motor?

[zro-1]

This is probably a silly question, and I've tried searching to see if it's been asked and answered before, but didn't have much luck with the results.

I am converting a single-speed bike that has a flip-flop hub—so I have both an 18T freewheel, and a 16T fixed gear. My question is that since a geared hub motor freewheels anyway, do I really need a freewheel sprocket on it? Could I just use the fixed gear? Are there any safety concerns with using a fixed gear on a geared hub?

If this has been asked before and you have better search-fu than I do, just posting the thread link as an answer is fine so we don't have to have the discussion over again.

Thanks.

 

[dustNbone]

Without one the pedals would still turn when the wheel turned, if that's what you're wondering. The motors freewheel only acts on motor, so that the wheel can spin freely without dragging the motor with it.

The sprocket that your chain is on would be directly fastened to the wheel hub/motor housing, essentially you'd have a fixed gear bicycle, which IMHO is about the dumbest, least safe thing you can ride anywhere, ever.

But that's just my opinion.

 

[zro-1]

OK. That makes sense. My current bike is a mid-drive, so I'm not familiar with hub motors firsthand. I'll be sure to use a freewheel on this build then. Glad I asked instead of finding out the hard way.

 

[JohnT818]

With a flip-flop hub, you reverse rotation of the wheel when you flip it, right? That won’t work with a geared hub motor as they’re directional. It might work with a direct drive hub.

 

[Chalo]

essentially you'd have a fixed gear bicycle, which IMHO is about the dumbest, least safe thing you can ride anywhere, ever.

But that's just my opinion.

Not just your opinion. Fixed gear bikes were abandoned over a century ago for very good reasons. They were kept around for certain kinds of racing, sort of the way open wheel cars or brakeless speedway motorcycles have stayed with us. But fixed gears were a bad idea as soon as the first freewheels and coaster brakes arrived. That didn't change when hipster dorks discovered them in the '00s.

In the case of a hub motor, there's an extra layer of peril, because hub motors don't have fixed gear lockring threading. Reverse torque at the pedals can cause the sprocket to unscrew, possibly disconnecting the pedals from the wheel entirely.

 

[dogman dan]

Penny farthings were abandoned a long time ago too, for similar good reasons. But some still want to ride them anyway. Same deal with fixies off the cycle track.

Anyway, your risks, your choice. Ride what you like, but unfortunately, with the hub motor it will unscrew the gear when you brake fixie. So put on the single gear freewheel.

 

[zro-1]

My apologies, the only reason that I mentioned the flip-flop hub was to mention that I had available both a fixed gear and a freewheel here at hand. I didn't intend to flip the electric motor. Just that I had a choice of gears to use.

I had gotten confused when I was reading that geared hub motors freewheeled, but now I understand that the wheel itself will freewheel, but the rear gear is locked to the hub motor. I definitely wasn't intending to lock the chainring and pedals to the hub motor's rotation. On my current bike I've only ever used mid drives that had freewheeling pedal arms, so that part had thrown me off also. I was confused about what part needed to freewheel and what didn't.

I definitely get it now though. The rear gear spins with the hub motor, so if you don't want the pedals flying around bashing legs, you need a freewheel back there to allow the motor to spin faster than you're pedaling.

Thanks again for all the input gang.