Originally Posted by
TiHabanero
One hears it all the time, and the experts proclaim it, however I have not been able to find any studies that demonstrate the superior fatigue resistance to breakage of double butted spokes. Please, does anyone have access to any real world testing of double butted spokes vs. straight gauge spokes when laced into a wheel?
Pillar Spokes doesn’t present testing in a laced wheel but they appear to have measured the breaking strength of all of their various spokes. They likely used some version of a machine like an
Instron tester. You have to click through all the spokes to see the data. Comparisons of the various strengths means flipping back and forth between several pages so it’s not the easiest to use but it’s the only real data I’ve ever found.
I have screen captured some of their graphs in the past.
Straight gauge
Image 5-11-18 at 1.41 PM by
Stuart Black, on Flickr
Double butted
Image 5-11-18 at 1.44 PM by
Stuart Black, on Flickr
Triple butted
Image 5-11-18 at 1.43 PM by
Stuart Black, on Flickr
You can see a clear increase in strength with butting and with increased head diameter. Looking at the 2.0mm spoke, going to a 2.0/1.8/2.0mm (1415 on graph) there is an about a 10% increase in strength. Going to a 2.2/1.8/2.0 (2018 on graph), there is a 22% increase in strength over a straight spoke. Pillar makes a 2.4/1.8/2.0mm quad butted spoke that has a breaking strength of 340 kgf or 25% greater strength than single butted.