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  1. #1
    Junior Member Vbled1's Avatar
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    Need some advice on future build, 29er hard tail single speed

    This coming fall I'm going to have a 1-2 mile commute to and from school, maybe a little more (I sound really lazy). I'm moving and not bringing a car with me. I want to build an electric bike. I'm not new to bikes at all just electric kits etc. I've been doing a lot of reading and think I'm headed in the right direction. I want to get a 29er hard tail, single speed and put an electric kit on it. I want to run an electric hub motor in the rear not the front which would be easier.... As I've been looking at kits I haven't seen if a single gear hub is interchangeable with let's say the standard 6 gear on kits I see a lot. Most kits I see don't come with any freewheel and they are just pictured. So is it as simple as finding a kit with measurements that will work my drop outs and then just adding a standard single gear freewheel like on a bmx bike? Thanks for any input. I'm looking at a 36v 750w kit at the moment.

  2. #2
    Senior Member chas58's Avatar
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    No one here has ever built a kit with a single speed bike because it requires a 120mm axle and the kits are 100mm for a front kit or 135mm+ for a rear kit. Best to use a front hub, or rear of a multi-speed bike (see my build).

    I'm trying to build a rear hub for a single speed frame, but its not going to be very straight forward.

  3. #3
    Junior Member Vbled1's Avatar
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    image.jpgimage.jpgimage.jpgThanks for the response chas. if its just the axle size can't I just enlarge the drop out to accept the axle, then reinforce it. I weld quite a bit. Or is it a problem of threading on the single freewheel?
    Last edited by Vbled1; 04-30-13 at 12:38 PM. Reason: Add pictures

  4. #4
    Senior Member chas58's Avatar
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    It is the width of the drop out (width of the motor). If you use a tiny 250W motor and are willing to futz around and fabricate, I think it can be done (that is what my plan is at least). Maybe your drop out is 135mm? All the single speed bikes I have seen are 120mm and can't fit a road wheel in that. If your bike is one of the ones that can accept either a single speed or a traditional geared road wheel, its no problem. If it was built as a dedicated single speed frame (i.e. 120mm wide rear axle), nothing off the shelf will be a direct bolt on.

    It all depends on the width of your frame at the dropout.

    And yes, you will have to figure out how to get the chain line correct. Most of the hubs take ancient screw on cassettes, although with the interest of the Europeans and Americans they are starting to make hubs that accept the slide on shimano cassettes. Cute makes a small one (250watt) and Bafang makes one that can take 500-1000 watts. They are labled CST (for cassette I imagine). The cassette ones are 135mm (or wider) naturally.

  5. #5
    Junior Member Vbled1's Avatar
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    Yea it seems like it would be much less of a headache to go with something along the lines of a mongoose sabrosa or asphalt, with the multiple speeds. I'm going to call the manufacturer though because both these model bikes are available in a single speed I believe. Maybe just the sabrosa actually, but my point is that possibly a bike that comes single or multiple speed may use the same hub size- seems more cost effective.

  6. #6
    Senior Member chas58's Avatar
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    Yep. And, with many hub motors builds you only need one speed, as the torque of the motor replaces (overpowers) the lower gear ratio's

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