Originally Posted by
Scooper
The critical measurement to determine if you can reuse the old spokes with the clincher rims (assuming you're going to reuse the old hubs that were used with the tubular rims) is the Effective Rim Diameter (ERD). If the tubular rim and the clincher rim are both in the spoke length calculator databases (like
spocalc) and they both have the same ERD, you can reuse the spokes. If the ERD difference between the tubular rims and the clincher rims is more than a millimeter or two, it's unlikely you can reuse the spokes; they'll either be too short or too long (you'll bottom out the spoke threads on the nipples before achieving adequate spoke tension).
If the ERD of one or both rims isn't in the database, you can measure the ERD:
Instead of cutting the spokes so you have a large gap andf three items all to keep straight, use two uncut spokes (of say 300mm but measure them), thread the nipples so that the top of the spoke is flush with the top of the nipple put them in oppoisite holes and measure the small gap you'll have. add that to the length of the two spokes and you have your ERD.
If the clincher is a same style rim (i.e. both are box style non-aerao, etc.) then the ERD should be very close. up to 2mm should be ok, larger than that difference and either they'll be too short na and might fail or be too long and won't tension up enough.