Reusing spokes:

From: Jobst Brandt

There is no reason why you should not reuse the spokes of your relatively new wheel. The reason a bike shop would not choose to do this is that they do not know the history of your spokes and do not want to risk their work on unknown materials. If you are satisfied that the spokes are good quality you should definitely use them for you new wheel. The spokes should, however, not be removed from the hub because they have all taken a set peculiar to their location, be that inside or outside spokes. The elbows of outside spokes, for instance, have an acute angle while the inside spokes are obtuse.

There are a few restrictions to this method, such as that new rim must have the same effective diameter as the old, or the spokes will be the wrong length. The rim should also be the same "handedness" so that the rim holes are offset in the correct direction. This is not a fatal problem because you can advance the rim one hole so that there is a match. The only problem is that the stem will not fall between parallel spokes as it should for pumping convenience.

Take a cotton swab and dab a little oil in each spoke socket of the new rim before you begin. Hold the rims side by side so that the stem holes are aligned and note whether the rim holes are staggered in the same way. If not line the rim up so they are. Then unscrew one spoke at a time, put a wipe of oil on the threads and engage it in the new rim. When they are all in the new rim you proceed as you would truing any wheel. Details of this are in a good book on building wheels.

The reason you can reuse spokes is that their failure mode is fatigue. There is no other way of causing a fatigue failure than to ride many thousand miles (if your wheel is properly built). A crash does not induce fatigue nor does it even raise tension in spokes unless you get a pedal between them. Unless a spoke has a kink that cannot be straightened by hand, they can all be reused.