Aero wheels? How aero?
 

So we all know how much wheelsets weigh. Manufacturers prominently advertise weights. (even if they exaggerate) If you're looking for a set of climbing wheels, it's easy to find how some given wheelsets compare in weight.

What about aero drag? This data seems much harder to come by. The marketing hype would have us believe that rim shape can make a significant difference on overall drag. But where are the numbers? How does anyone pick wheels for a TT bike? Is there an an Aeroweenies counterpart to the Weightweenies website?

Uhm... Zip 303? Best Compromise, I think.

If weight is no issue, there is nothing faster than a Hed3 front / Disc rear.

It's much harder to put things in a water or air tunnel to measure aerodynamic drag, as opposed to simply owning a scale.

Besides, how do you quantify the exact aerodynamic drag for a given component, esp. when it's installed on a bike?

I don't know. That's part of my question. I assume it's possible based on the advertising claims that wheels are critical to aero-ness. If they can make those claims, there must be some numbers somewhere. You'd think.

An honest question: Based on what? Where are you getting information?

I'd imagine there are ways to determine how aero a component is, but only relatively (i.e. wheel A is more aerodynamic than wheel B by simple windtunnel findings). If there were reliable drag numbers available, I'm sure the manufacturers would be spouting them off about as much as they spout off the weight of a specific component.

And a good question. With respect to my statement, the answer is "Because I said so" as my father used to say. Sorry. There have been numerous tests done over the years.

A disc in the front and rear is actually the best. This is universally accepted based on data from testing - a disc wheel is unbeatable. However, a disc in the front isnt possible for control reasons.

Enter the Hed 3. It has a deep rim (60mm-70mm ish I think) and aero "spokes". There is no spoked wheel that can be used on the front that is as aero as the hed 3, without being to deep to be safe and controllable. If you search for a while, you can find several of these studies and reports. I have seen several, but I dont keep track of them. Analytical cycling is a good place to start (google it). There are yaw angles where the Hed 3 can be beat by a spoked wheel, so the arguement is not universal, but in straight-on and low winds, it is the reference.

Within these arguements, there are sub arguments stemming from lenticular shapes and dimples, etc. These claims are probably true, IMO. They make sense from a physics standpoint, but they have not really undergone the test of time to see for sure.

In that regard, there isnt really a 1 right answer in the area of aerodynamics. It depends on a variety of things. For instance, a wheel may in theory be better than another, and on most frames, will be in real life tunnel testing. However, on a certain bike, the air turbulence may interact with the frame or fork of the bike that makes that one particular combination an erroneous data point (This is just an arbitrary example). This is also why there is no "perfect" bike fit or aero-position. Only a guidline that will get you close.

In like manner, the same is true for aero. Deeper is better (therefore disk is best). Hed 3 is generally better, due to the benefit of the Hed 3 "spokes" vs regular or bladed spokes, even vs deeper non-disc rims.

If it looks aero it probably is. If it looks more aero then it probably is.
Of course, sometimes it isn't. So there you have it.

For free www.zipp.com under aerodynamics/rim shpe. For a little money, www.biketechreview.com

I tend to agree with most of what you said, particularly since I TT with a HED disc and a HED 3.

However the Zipp people would take exception with the assertion that there is no spoked wheel as fast as a HED3. Zipp claims that the 808 is faster in real world conditions than the HED3.

http://www.zipp.com/portals/0/techno...comparison.pdf seems to be exactly the type of information I'm talking about. Especially the last page.

Edit: More good stuff: http://www.carbonsports.com/LW_Test_Tour2002.lasso

most manufactures claim a savings of about 11 watts which is around .4 mph faster. Doesnt sound like much, and it isn't But it can be the difference between staying in the break, or getting flicked

i think hed posts info on drag at different angles.

Isn't it true that at certain wind angles the deeper Zipp wheels actually have a sail effect and will spin on their own?

In fact if you tack across the road at the correct angle you don't even have to pedal

I'm pretty sure aero wheels just look cooler/faster, so you go faster... I'll have to find those pesky references on this data, but I'm pretty sure that's it.. it works for me at least :D

HED's own data show that the Stinger and Jet (deep wheels) are significantly faster than the HED3between 5 and 10 degree yaw. In this way, it would be impossible to say outright which wheel is better unless one knew the course conditions. If there is no headwind or there is sigificant crosswind, the HED3 would be better. In the common situation of 5-10 degrees of yaw, the deep wheels would be better.

Another consideration with trispokes is their interaction with different forks. Some testers have demonstrated that there is a significant "pulse" of air every time the large blades pass through the forks. This pulse varies depending on the size and shape of the fork. It is noteworthy that although Discovery/USPS have used the H3 for quite some time, Hincapie and others have started to add the deep Stinger wheels to their arsenal.

Basically if you're not racing, you don't really need to be concerned with 40+mm deep section aero rims.

Thanks for clarifying. I did not make that point as clearly as I should have amongst the rest of my disertation. That is exactly right. That is where I was going with the sentence below.

"There are yaw angles where the Hed 3 can be beat by a spoked wheel, so the arguement is not universal, but in straight-on and low winds, it is the reference."

I'm certainly not in the market for >$1k wheelsets, and am only a lowly cat 4, but I have a few wheelsets. I'm planning to do a few TTs this year, so I'm just looking for general information.

The Tour magazine does a wheeltest measuring aerodynamics of wheels, this is a list of watts spent for a given wheel at either 25 or 30mph listed from best to worst: Ritchey Carbon, Easton, Vuelta and CKT all use an undimpled 404 rim.

Zipp 808 18.1
Ritchey WCS Carbon 19.3
Hed 3 19.7
Vuelta Carbon Pro WR 20.8
Easton Tempest II Carbon 21.6
CKT Splendor 21.7
Mavic Cosmic Carbone SL 21.9
Shimano WH-7801 Carbon 50 22.9
Campagnolo Bora G3 23
Rose Aerospoke 23.0
Corima Turbospoke 23.1
Bontrager Race X-Lite Aero 23.4
Fulcrum Racing Speed 23.7
Gipiemme Carbon 5.5 24.1
Tune Olympic Gold 24.1
Shimano WH-7801 Carbon 24.4
FRM FL-R 23 SD Aerolight 24.6
Corima Aero 24.7
Lightweight Obermayer 24.8
Xentis Mark 1 25
Citec 3000s aero 25.5
Shimano WH-R560 26.1
Lightweight Ventoux/Classic 27.3
Campagnolo Eurus 27.8
Tune Skyline 28.1
FSA RD-600 28.7
Mavic Aksium Race 30.0
Citec 3000S 30.6
Ambrosio X-Carbo 31.5
Campagnolo Hyperon 32.1
Mavic Ksyrium ES 33.2

Those #'s look pretty reasonable IMO. Possibly a link? I am curious about the experimental setup.

Jamie Wilson, you make a lot of big generalizations without DATA. The Hed 3 has a 55mm rim, and it's performance can vary greatly depending on your fork choice. I think still very disputed that a Blackwell 100, Zipp 808 or Jet 90 is the equal to if not better than a Hed 3. Edit: I was typing while you were.

The tests I showed the Hed3 was inferior to the 808 and a Ritcheys version of the 404

Part of the thing with a HED3 vs. a Stinger 90 is that the stinger is fastest with a 21m tire and the Hed3 with a 19mm tire. Also, the Hed3's that Disco used last year had 90mm rims on them not the standard 55mm rim. As for that pulse, you can hear it but it really doesn't seem to matter. I think that's more a remark of Zipp's because they had to blame something on the failure of their 3 spoke wheel (the Zipp 3000, ever seen one?). 90mm carbon tubulars are loud too, it's more a function of their material naturaly amplifying sounds (road noise, freehub engagement, and so on).

Are you saying I'm wrong? Do not 21-23mm tires roll faster?(yes) Why do you think the wide spaced Kinesis aero fork was used by Trek for so long, it is a great design for Hed 3s and its "pulse".

I presented independent data, from a wind tunnel saying there are indeed 2 wheels faster than a Hed 3.

A poorman's pseudo "windtunnel" is actually quite easy to simulate. Find a steady grade hill where your terminal velocity is 25 to 30mph. Simply use you cyclometer to indicate what your terminal velocity is. To do A and B comparisons just compare the 2 sets of readings. Several readings in each setup would be preferred. Of course, wind conditions and traffic flow have to be at minimum. One needs be careful to duplicate your level ground riding form and spin the cranks in a low gear to simulate the air over the legs, but be careful not to apply any torque to the wheels.

For the tech weenies one can make this even more instructive by using 2 -3 different grade hills. For a given setup find the respective terminal velocities and then back out the rolling resistance which can reasonably be assumed to be linear with speed, whereas the air drag with be a function of speed squared. If you measure the grade of the hill then you can relate that back to the actual drag force and rolling resistance force. A further step in the process can be use the same hills and ride them up and use the average speed to calculate your output power. Of course, if you have a power meter then you already have it.

I agree with that statement, and the data you posted. However, comparing a 808 or blackwell 100 to the Hed3 is a bit of a stretch when winds are considered. They are both near-disc wheels, especially the Blackwell. The Ritchey is hard to explain, but I do believe it.

As also stated above by several, including myself, there is no 1 fastest wheelset. It depends on the course, conditions, and the rest of the bike (fork as you mentioned). But for the best all around fastest wheelset (wind stability is a critical issue), the data that I have seen over the years points to the Hed3 with a disc rear.

The Tour Magazine Wheel Test in French

http://www.rouesartisanales.com/article-4854616.html

Some more data to throw into the fray (sorry for the formatting) H3 beats 404 here. The deep comes in #1.

Cobb Wheel Drag Data (lbf)
Yaw (degrees) 0 5 10 15
Rolf Vector 0.318 0.425 0.402 0.358
Hed-3 0.223 0.223 0.117 0.109
J-2 0.259 0.285 0.336 0.320
Deep/S90 0.216 0.198 0.086 0.081
ZIPP 404 0.255 0.243 0.142 0.125
Shimano-23 tire 0.261 0.306 0.314 0.373
Helium 0.399 0.380 0.445 0.414
Spinergy Spox 0.445 0.494 0.652 0.596
Lew 0.279 0.284 0.251 0.207
Std box rim 32* 0.401 0.408 0.402 0.414
Jet 0.252 0.296 0.254 0.267
The data for this table were taken from a table published at John Cobb's web site, www.bicyclesports.com. Andrew Coggin, commenting in rec.bicycles.racing on the data in that table, said, "The wheels are tested in the low-speed A&M wind tunnel ... in a purpose-designed fixture mounted on the tunnel floor (picture the typical roof wheel rack). A recessed roller spins the wheel at 30 mph." He further commented that the values are in lbf at 30 mph at standard air density, 1.226 kg/m3, and that the wheels were tested with Conti Grand Prixs tires.