I fail to see how a 15g spoke in a slightly larger hole creates any additional cyclical stress on the bend. Considering that there's always tension in exactly the same direction relative to the hubshell, are we to assume that the spoke head rocks in response to the cyclical load variation? Don't forget that any given amount of rocking will also create greater cyclical stress variation in a thicker spoke's bend than in a thinner one. Also consider that spokes of any diameter are critically designed to conform optimally (with minimal flexing) to spoke flanges of specific intended thickness, but this has nothing to do with spoke thickness.
I've built a lot of wheels and actually prefer 15G to all others. Less windup than with butted spokes makes for a faster build. There's their lower price and weight, and these also seem to have a proper amount of elasticity for a lot of different applications. Their added bending flexibility vs 14G spokes also makes building wheels a little easier, as does a freer fit through the spoke holes.
What's not to like? There are some applications where lighter or thicker spokes will prove superior, but I have yet to break a single DT, Sapim or Wheelsmith 15G spoke!
Pre-stressing pairs of spokes after tensioning is the best way to assure the relief of residual stresses in spokes, rims and flanges and helps to maintain tension over time.
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Earle Young wrote:
>I respectfully submit that 15-gauge, straight gauge spokes present even more issues than straight 14 gauge. One of the common failure points for spokes is at the bend, especially if the spoke head has any room to move. Since most hubs have holes big enough for 14-gauge spokes, there is more room for the spoke to squirm and develop fatigue. And any straight-gauge spoke, whatever the thickness, will transmit more destructive force to the rim and the elbow than a butted spoke of the same elbow/thread thickness. The only time I vary from 2.0-1.8-2.0 butted spokes is where a rear hub has holes large enough for the DT Alpine 2.3-1.8-2.0, or for a light rider, if I can find an early production, NOS Record hub with holes so small that a 1.8 mm spoke is a tight fit -- and it's been 25 years since I have seen one of those.