The best in aero anyway… by a healthy margin. I’ve not seen a cross-section of this rim but from the description it sounds like a big fat oval… ie similar to the Zipp Firecrest concept. It seems like a very unaero shape to me… but I guess not. The other funny thing is that Zipp and Hed have been at the top of the aero game for many years with their toroidal rim shapes, and now that the patent on that has run out they are making a completely different shape… that is even better. I’m impressed.
They tested the wheels with a 21mm Corsa CX… which makes the results even more surprising, since the Hed is the only one designed for wider tires. They did a sweep from 25 down to zero yaw, and the Hed was the only rim to have flow attachment at 15 deg… which resulted in a drag of only ~30g, compared to 150-200g for all the others. At 10 degrees things tighten up a bit, but the Stinger is still the best… and it’s the best at every angle from 0-20.
Why is it important? The effects are known and predictable enough to extrapolate the values for lower speeds from the standard 30mph wind tunnel speed. The equation(s) are fairly straightforward.
I would really like to understand why Zipp 808 got a better score. What else was used in the comparison. It could not have been price. Bearings? If you use FR I would think they would be even.
I assume the Stinger was the 09 - 10 version. I don’t believe there is a new one with a new shape.
It is interesting that on the HED web site they indicate the Stinger 9 was designed for optimal aerodynamics with a 23mm tire. They go on to say the warranty will be voided if you use anything less than a 23.
Yet in this test a 21mm tire was used. In a post earlier this year HED indicated the test results on their web site were done with a 21mm tire.
Something is up with this. Would be interesting to see test results with a tire that does not void the warranty.
Fair enough. I haven’t done enough research to extrapolate the data myself, thus I was curious.
Just because a wheel is the fastest at 30mph and 15* means that it is also the fastest at 20mph and 15*?
Yes. This is because of how yaw angle is derived. Remember that that 30mph and 15* doesn’t mean that the wind is coming at you at 30 mph and 15*. It means that you’re doing 30 mph, and that the wind is coming at you at somewhat more than 15*, but the two vectors add up to 15*.
According to this, at 30 mph (which is fast), a 10 mph wind has to be blowing at 55* from central to show as 15* yaw. However, at 20 mph, that wind only has to be 7.5 mph to have the same yaw angle. So, here, yaw is much more important than speed.
I would really like to understand why Zipp 808 got a better score.
They ranked by the following criteria with no regard for absolute differences… ie if a wheel was first it got 1 point and last got 6 points… even if there was little difference between them. Plus as you can see there are 3 scores for “weight/inertia” which makes this category three times as important as aero to the overall ranking. So the ranking is useless, IMO. For TTs only the aero really matters for these.
Aero
Weight
Front wheel stiffness
Rear wheel stiffness
Front wheel inertia
Rear wheel inertia