I am trying to learn how to build a wheel and I am running into a problem measuring my spoke length. I have used the various spoke calculators only to find they neither have my Rim ( Mavic x223 Disc) or Hub (Shimano Deore FH-M525). When I measured my Spoke length it comes out as 320 mm. Nobody seems to sell a length this long. I measured to other friends spokes and they also have 320 mm spokes. I am obviously doing something wrong. Can anyone help me. Thank you..