Spoke shape
One of the key drivers of the decreased spoke count movement was that early testing showed large drag decreases with decreased spoke count. Round is a very non-ideal shape for anything which must be propelled through the wind, and the early testing was all conducted using varying counts of round spokes, thus reducing the spoke number could have lead to large drag reductions in a wheel. Tires are essentially round and the only way to improve their performance significantly is to control the downstream airflow in such a way as to reduce pressure drag. Rim shape can help here but with spokes, however, we do not have the luxury of being able to build structure onto the trailing edge as we do with a rim. Spokes are generally designed primarily for structural properties including fatigue and ultimate strength followed by weight, with aerodynamics being more of an afterthought coming about in the late 1980’s and early 1990’s.

The first aerodynamic spokes were bladed; essentially, a round spoke was smashed in the center to form a thin rectangular cross section. This was an improvement, but hubs now had to be slotted to accept these special spokes, and they tended to be heavy as only straight gauge spokes were generally bladed. The next improvement came in the form of ovalized spokes. These had the advantage of not requiring slotted hubs, but were generally still made from straight gauge wire, and were still heavy. The beauty of the oval profile is that it is very aerodynamic over a wide range of wind angles and conditions. Bladed spokes are more aerodynamic than round spokes at most every possible condition, however, they do add some side force to the wheel in a cross wind, whereas oval spokes tended to yield an aerodynamic improvement and reduced side force. In 2002, a radically new spoke from a small Belgian company had taken the pro peloton by storm. The spoke was the CX-Ray, a double butted spoke, ovalized through coining, and post heat treated. The test results showed a more than doubling of fatigue life, and a slight improvement in aerodynamics over the existing 14 gauge ovalized spoke. The aerodynamic benefit came with a weight benefit as well since these spokes were ovalized on a 16 gauge butted section, so Sapim had produced an aero spoke with the weight of a superlight butted spoke.