Motor to fit nine speed cassette?

[cirrus18]

Motor to fit nine speed cassette?

As I didn't want to modify my bike in any way I had had been planning to build an electric trailer to give me assistance up hills. Looking into it further, it is not so easy as I first thought, so perhaps I will modify my bike.
At the moment I have a nine speed cassette and was wondering if there is a motor that would fit this size cassette . Failing a 9 speed what about a 7 speed. I suppose I could always change to a smaller cassette if that was the only option.

Have carbon front forks which rules out a front motor I think.

 

[flecc]

Motor to fit nine speed cassette?

As I didn't want to modify my bike in any way I had had been planning to build an electric trailer to give me assistance up hills. Looking into it further, it is not so easy as I first thought, so perhaps I will modify my bike.
At the moment I have a nine speed cassette and was wondering if there is a motor that would fit this size cassette . Failing a 9 speed what about a 7 speed. I suppose I could always change to a smaller cassette if that was the only option.

Have carbon front forks which rules out a front motor I think.

Hub motors can't use any cassettes, their spindle size is 12 mm and the cassette system only accepts the normal bike spindle size of 10 mm. Hub motors have to use multi-sprocket freewheels instead. Unfortunately the range of these is very limited aand 8 speed is the absolute limit, and are as rare as hens teeth anyway.
.

 

[HarryB]

Have carbon front forks which rules out a front motor I think.

Cannondale Capo/Synapse and Claud Butler Urban 500 all have carbon forks I think. All can be successfully fitted with a front motor as in the Cytronex. I wouldn't want to fit something like a Heinzmann motor to carbon forks though....

 

[Tiberius]

Hi Cirrus,

Normally we get the question asked the other way round - what cassette to fit this motor?

As flecc says, though, with a hub motor, you will need a freewheel rather than a cassette, and getting a 9 speed one won't be easy.

Even if you could get one, there might not be room on the hub motor axle. As the number of gears goes up, the spacing between them goes down, so even a 10 sp cluster is not much wider than a 6 sp. But it is still a little wider and a lot of hub motors will need extra spacers and spreading of the bike frame even to go to an 8 sp.

Mostly, what people are really trying to do in these cases is to match the new gear cluster to the existing gear shifter. If you are prepared to change the shifter, then you can have a wider choice of motor and gears.

Here's another problem, though, when you get above 6 sp, Shimano, Campagnolo, etc tend to use different spacings, so you can't always mix and match components.

Nick

 

[cirrus18]

Many thanks for your answers guys. Is this what I want?

I suppose I would have to change the shifter to a 8 speed one.
I was thinking of getting a Bafang motor do you think it would fit it? Any suggestions of what I would need to get it all fitted would be most appreciated.

 

[daniel.weck]

I was thinking of getting a Bafang motor do you think it would fit it? Any suggestions of what I would need to get it all fitted would be most appreciated.

For starters:

http://www.pedelecs.co.uk/forum/electric-bicycles/4594-brompton-sparticle-latest-suzhou-bafang-motor-8-fun.html?highlight=bafang#post58635

Cheers, Dan

 

[Andrew harvey]

Simple answer No.
Most rear hub motors are limited by the axle lenght, Tongxins struggle with a 5 speed, some Bafangs will take up to 7, but at 8 speed your going to struggle.
The only motors to take 8 and 9 speed freewheels that I know of are the Bionx.
Airnimal should have 9 speed freewheels for their Moves, worth the phone call.
The Tongxin motor should drop into a pair of carbon forks, or you could swap them out for a pair of Cromo forks, I think they give a much nicer to ride.
If your going for a Bafang motor I think your going to need the larger BP version to get a bigger than 6 speed, but that from memory so I could be wrong.