I acquired a rim from my Brother in law the other day for use on a Tandem rear wheel build. It is a Sun 40 hole Chinook with a wheel smith decal on it but no other markings or numbers. It is in great shape but when I contact Sun/Ringle for the ERD, they have no specs on the older Sun stuff. Does anyone know how i can get this ERD so I can calculate the spoke length? Thanks in advance!