We design for the real world, and for the gravel roads in that world, people want to use 700x35-40c tires. It’s useless to put a narrow aero rim behind such a tire. You’d be adding the weight without the aero benefit of such a wheel as the airflow never really “sees” the rim.
After testing two dozen prototype wheels in the tunnel, the Discus 45 | 40 LTD was born. 45mm deep for good aerodynamics without excessive cross wind vulnerability. 40mm wide to match up those 35-40mm tires. The result is speed never seen before on gravel roads. And while the shape is optimized for the 3T Exploro, the Discus 45 | 40 LTD makes any gravel bike faster.
Our best aero shape was a knife-like 12mm wide at the pedal, significantly thinner than anything else in existence (cranks are usually 15-17mm at the pedal end). In the other direction, our desired profile was much deeper than usual.
The transition to the spider is another headache area. For structural and stiffness reasons, we want the spider to be integrated with the crank arm and fibers running through both. Yet we also want the chainring to be separated spatially from the drive-side crank arm (not one blended shape) to avoid aerodynamic blockage. The Torno spider offers exactly that and works in unison with the dedicated Wolf Tooth aero rings.