Will this work on 20" rim?

[waynesworld]

I want to buy a electric conversion kit for my bike but the smallest rear wheel that they supply is a 26" rim. I asked if they can supply a 20" rim with spokes and the fella said he just sells them he dose not know if that is possible. If I do buy the 26" rear wheel can I change the rim and spokes for a 20" one? and what size spokes would I need?

[nfmisso]

Maybe.

We need some specifications on the hub and the rim.  See: http://sheldonbrown.com/rinard/spocalc.htm for the measurements required. The ones shown in the pictures you posted are only sufficient to tell if the wheel will fit in a frame.

The 13.5cm (usually specified as 135mm) is the Over Locknut Dimension (O.L.D.), which should be within a millimeter or so of the spacing in your frame. Remove your current rear wheel, and measure the distance between the drop outs. Frames for larger wheels are more flexible on the O.L.D. vs frame spacing because the seat stays and chain stay are longer.

[waynesworld]

Thanks for the reply Nigel
The rim I want to use is 20" and the hub as you can see from the picture is 25cm in diameter.
So A: can it be done? and B: What size spokes would I need for it so I can order them at the same time as I order the hub and kit.
Cheers

[painkiller]

Just get this one
http://www.aosom.com/d-7698/20-Rear-Wheel-48V-1000W-Electric-Battery-Powered-Bicycle-Motor-Conversion-Kit-w-LCD-Display.html?gclid=CMmM2rjxocYCFQ2OaQodz-0B_g

[waynesworld]

I would but its out of stock and its about £40 more than the one I am looking at. If it only means I have to lace some new spokes that will only cost me a couple of pounds against an extra £40.

[painkiller]

you need 135mm rear spacing in your frame, you will need to know how many hole the hub will be to match with the proper rim. then calculate spoke length with the info Nigel provided. then see if the size is available somewhere or you will have to have them made to suit. without the hub and rim in hand, we cannot tell you what size you need. you have to measure the rim, hub, and use the calculator.