The are numerous posts/discussions concerning carbon rim shape. Zipp and Hed share the super-shape rights and make wheels accordingly. Various other companies apparently buy the rims from Zipp and Hed because they are so super. The shape is such a deal that both Zipp and Hed insist that you need just the right tire to make the aero magic work. If this is all true, Why are the drag numbers the same for both the Hed stinger and jet (in all rim depths)? I don’t think the jet has the super shape.
All of the Hed and Zipp wheels share the same Tordial rim shape. So do alot of others that buy rims from zipp (AC, Rolf, etc).
Oh and it is not so much the right tire as it is the right tire width. if you go too wide the air will separate from the rim and create turbulent flow causing drage to increase.
The Jet does in the 60, and 90, not sure about the 50.
The torroidal rim shape is in effect the closest thing making the tire the leading and trailing edge to a suboptimal airfoil. Now I know what you’re thinking, suboptimal airfoil? However this suboptimal airfoil does a great job with air passing over the inside edge of the rim as the leading edge, and with the trailing edge being the inside of the rim.
And actually the torroidal rim shapes work better with MORE tires than non-torroidal rims. A Stinger 60 or 404 with its rim width of 24-25mm, will do a better job with 23mm tires than a wheel that is 20mm wide and tapers to a V.
Whenever you see a V shaped rim imagine air passing over the point of the V first, and exiting off the tire(it’s not a very smooth transition or ideal if you consider that a Cervelo or Trek downtube is a good shape for bicycle speeds), because thats whats going on on the back end of your wheel if you own say a Reynolds.
What Blackwell has done to get around this is to make the nose of the rim rounded and blunt with flat sides. Which I would imagine works equally well as a leading and trailing edge. However, Zipp and Hed say that the bowed out nature of their rim keeps flow laminar at higher yaw angles than flat sided wheels like Blackwell. And again, with Blackwell, a 22mm(real world size) seems to defeat the purpose of an object that is only ~20mm wide.
These are not huge differences but why settle when you’re spending $1500-2500
According to the Hed site the jet 50 drag is equal to the stinger 50. So I guess the stinger toroidal shape is important unless the competing wheel is the jet (same hub, same spokes, same company, different rim).