• find out the erd (effective rim dimamiter, this is not 622 it is slighly less as it is where the nipple sits) the oln (over locknut distance) the flange dimiter and the flange to lock nut distance, goolge should be able to help you out for each of these, if not email where ever you are buying from and ask.

    I then use http://www.recumbents.com/wisil/spokes!.­asp there is also a exel with amny common hubs and rims with all the legths alread worked out that you can download see how you get on and come back to us.