Originally Posted by
kjaioqhbkqb
On the Wheelsmith website I only see DB14, not DH13 What's the difference?
Here's a link to the
DH13. DH13's have a 2.3mm head/bend with a 2.0mm shaft. A DB14 has a 2.0mm head, 1.7mm middle, and a 2.0mm end. The "DB" means double butted which means it has a narrower midsection.
DT Alpine III differ from the DH13 in that they have a butted middle section as well. The dimensions on the Alpine III is 2.3/1.8/2.0mm. That thinner midsection provides a bit more elasticity in the spoke. Sheldon Brown discusses the benefits of the thinner midsection
here.
Double-butted spokes are thicker at the ends than in the middle. The most popular diameters are 2.0/1.8/2.0 mm (also known as 14/15 gauge) and 1.8/1.6/1.8 (15/16 gauge).Double-butted spokes do more than save weight. The thick ends make them as strong in the highly-stressed areas as straight-gauge spokes of the same thickness, but the thinner middle sections make the spokes effectively more elastic, allowing them to stretch (temporarily) more than thicker spokes.
As a result, when the wheel is subjected to sharp localized stresses, the most heavily-stressed spokes can elongate enough to shift some of the stress to adjoining spokes. This is particularly desirable when the limiting factor is how much stress the rim can withstand without cracking around the spoke holes.
He also has this to say about the thicker head on spokes
Since spokes use rolled, not cut threads, the outside diameter of the threads is larger than the base diameter of the spoke wire. Since the holes in the hub flanges must be large enough for the threads to fit through, the holes, in turn, are larger than the wire requires. This is undesirable, because a tight match between the spoke diameter at the elbow and the diameter of the flange hole is crucial to resisting
fatigue-related breakage.
I noticed that when I first started building with triple butted spokes almost 20 years ago. The spoke is tighter in the hub so there is less movement of the head as the spoke travels around the wheel. When the spoke hits the bottom of the wheel, the rim deforms and deflect upward (slightly). There is a momentary relaxing of tension on the spoke and, since the other spokes are pulling on it, it moves upward, then downward, then upward, ad infinitum. This puts stress on the head and if the head can move, it puts more stress on the head. The more weight on the bike, the more the rim deforms and the more stress is put on the head. Frankly,
all spokes should 2.3mm heads.
If you really want to get deep into the weeds, here's
an article that explains why triple butted spokes are a good thing. Ric has a whole bunch of other articles on wheel building that are worth reading as well. I still use and teach his
building method from 1986 Bicycling Magazine (back when it was useful). He, by the way, was the founder of Wheelsmith.