Originally Posted by
AS Collie
A mechanic friend of mine told me that you didn't really need two different spoke lengths for the rear wheel, as I had been told. In fact, he claims to often build the front and rear wheels with the same length spokes (he showed me a set of some retro Campy record hubs he'd just built up that he said had the same length front, rear [drive and non-drive]).
With "retro" wheels the difference between the DS and NDS rear spokes is not as great as it is with modern 8, 9, 10, and 11-speed rear hubs because the DS flange offset is not as great. This also means that the spoke tension differential is not a great. If using long spokes the greatest risk is running out of threads "bottoming out" before reaching sufficient tension. When this happens your options are to replace the DS spokes or cut more threads, or lower the NDS spoke tension to a dangerous level in order to center the rim. I've had custom built wheels as well as machine built wheels bottom out the DS nipples because the spokes were too long. When ordering spokes I always round down from the calculated lengths and reduce an extra 1mm on the DS rear.
Cutting the ends off of spokes is not a problem, running out of threads is.