Similar to the Discus 45 | 32 LTD, the Discus 45 | 40 uses the NoseTail design to squeeze 60mm deep rim performance in a 45mm profile.
By definition rim design is a compromise, because it whatever shape is aerodynamic on the front half doesn’t work so well 180 degrees later when it’s backwards. The NoseTail shape was developed by the legendary Dave Kennedy (an aerodynamics professional for over 50(!) years) and 3T’s Head of Design Gerard Vroomen. The NoseTail actually sacrifices some performance on the front half of the wheel in favor of working better on the back half.
Not only do the two effects cancel each other out, but the resulting shape also requires less rim depth and better guides the airflow from the rear of the front wheel onto the downtube. This is particularly helpful on the Exploro RaceMax where the downtube is positioned in close proximity to the front tire.