Damn… I need to expand my vocabulary…
Now correct me if I am wrong, but from what I can tell of the new rim shapes(Zipp FC and FLO): the trade off for gain in low yaw angles when going deeper is almost not worth it at all when you compare the better performance of shallower rims at higher angles.
The same is NOT true about older style (planet x/ generic chinese carbon) rims. Correct?
So for older style rims, deeper is almost always better in any condition…
the more advanced shaping does not really give anything away at lower yaw, but there are many wheels that perform well at that level at low yaw.
well shaped deeper rims are still going to manage the air better than less shallow rims. the problem with going deeper also means that you have to go wider and at the increased depth youre more sensitive to cross winds.
look at the 808 vs the 404 firecrest, deeper is going to be faster if you shape the rim correctly.
http://media.bontrager.com/images/features/201108_aeolus/bontrager_aeolus_d3_wheels.pdf
I think you might need to expand your vocabulary prior to writing the question.
Short answer - the shape of a rim like Firecrest allows a shallower rim to be faster than a deeper rim of a “deep-V” type shape. But that’s not really anything new. It’s just the degree to which it is true. Many of the old, even very deep (say 90mm) V style rims were slower than the toroidal and hybrid toroidal 404s. It’s just now you get wheels like the 303 that are even faster than those deep rims.
For any given rim profile, deeper is better (ex. the 808 will be faster than the same series 404). For different wheelsets, you can’t compare directly because their profiles are not the same shape (ex. no guarantee a 90mm rim from company A will outperform a 60mm rim from company B).
The newer profiles tend to be faster (ex. Firecrest 404s are faster than toroidal 404s)…technology marches forward.
The newer profiles (FC & FLO for example) tend to improve less with increasing depth than the older designs. Deeper is still faster, but the gain is smaller.
Let me try and answer your questions based on what I have learned designing our wheels…
Damn… I need to expand my vocabulary…
Now correct me if I am wrong, but from what I can tell of the new rim shapes(Zipp FC and FLO): the trade off for gain in low yaw angles when going deeper is almost not worth it at all when you compare the better performance of shallower rims at higher angles.
Low yaw angles (let’s assume you mean 0-5 degrees) haven’t typically been where you see your biggest aerodynamic gain. Take a look at the aero data published by the different companies. At 0 degrees, most “aero” wheels have relatively the same amount of drag and are within about 30 grams of drag of each other. Even up to 5 degrees of yaw, most aero wheels will follow roughly the same aerodynamic pattern. HED has an interactive aero data graph that you can play with to see what I’m talking about. Even if you look at our data you can see that our FLO 60, FLO 90 and FLO DISC are within 15 degrees of yaw up to 5 degrees and follow nearly an identical aerodynamic pattern.
http://i1210.photobucket.com/albums/cc409/flocycling/FLO_Aero_Data.png
Where you really start to see an aerodynamic advantage is between 5 and let’s say 25 degrees of yaw. The reason (or at least one of the reasons) behind this is something know as “side force” or “lift”. In order to gain an aerodynamic benefit, you need to generate side force. In order to generate side force you need a yaw angle. If you want a better explanation of side force and lift let me know… but in short, the more side force a wheel can generate the better. The newer shapes are helping generate more side force and in my opinion, aerodynamic wheel design is trending towards a balance of depth, width, and shape… not simply depth.
The same is NOT true about older style (planet x/ generic chinese carbon) rims. Correct?
The shape of older style wheels do not allow them to generate as much side force as the new shaped wheels. Additionally, the shape of older style wheels cause them to handle rougher in side winds due to a lack of balance. I think spoke length definitely had something to do with why “deeper = more aero” in the past. Spokes create a lot of drag and if you went deeper, you had less total spoke length, which in turn meant more aero.
So for older style rims, deeper is almost always better in any condition…
That’s tough to say. I think there are far to many variables to say deeper is always better
I hope that helps,