I'm rebuilding my front wheel after yet another spoke explosion.
Two broke on a ride, and when I deflated and removed the the, two more broke, including one that wasn't covered by rim tape (I had partially removed the tape to repair the 2 broken spokes, which were adjacent) and shot the rim end clear across my garage! I was damn lucky not to have been leaning over the rim, or it could have taken an eye out.
These spokes are NOT overly tensioned (using Park Tools' tensiometer, they are about the same as my wife's Thorn-built wheels). They are black though, and Dave Whittle has previously indicated on this site that their turnover for black spokes is much less than for silver. (Disclosure: I built my wheels from SJS-supplied spokes, whereas my wife's wheels were built by Thorn. However, I'm assured by several wheel builders in my area that my wheels are built properly.)
Thus, my suspicion is that they are old stock from a period several years ago when there was substandard SS wire coming out of China. A friend who manufactures very well specced touring bikes here in Australia was surprised that the problem was with Sapim spokes, but he related that he was aware of the bad wire. He recommended that I switch to DT Swiss straight spokes (non-butted, Champions), which I have ordered.
Some of you may recall that last year, Sapim responded to my complaint by sending me over a full set of Force spokes for each wheel. Upon advice from Dave and the Rohloff and SON websites, I have not installed these as they are slightly larger at the hub end than recommended, but ordered a full set of new Race spokes for each wheel. Some of these have now broken.
I guess I could have gone to silver spokes for better results, as they would presumably come from a fresher batch, but I really want to put the issue to bed once and for all. My bike maker friend insists the problem is not with the finishing process, so I want to stay with black spokes. The added weight from the non-butted spokes is expected to be minimal (less than one spoke on each wheel?), and at a straight 2.0mm, they should be stronger than the Race.
Watch this space!