Why all the different variables between the two tests? Different speeds, different tires, different bikes... Unless this is some standard way to do things that I am ignorant of, it looks like potential cherry picking of data. Thankfully, there are plenty of aero experts on here that I'm sure will offer some valuable insight on this.

Without knowing, my Bet is that it really depends on your speed and average yaw angle. If you’re going 30kph any disc is probably faster than a deep section, worth the premium? (Depends on the person). And at lower speeds it probably doesn’t matter as much. A tests would probably benefit cheaper Chinese open moulds if cost is a factor, meaning that wether you’re using a disc a not has a bigger impact than which disc it is. But this is just speculation from my side

They were tests done at different times. The 2nd test is more recent I think and they probably chose the tyre and the Hed wheel as they are some of the most popular currently used on the UK TT circuit. When the early test was done Conti were the go to tyres of choice. I think they may even have been done at different venues and possibly by different aero experts - so probably best to look at each in isolation. I know they produce their wheels in a Tubeless version so it is possible the 2nd test was also done Tubeless while the 1st test wouldn't have been as it was before Zipp made their wheels Tubeless compatible.

I think the Plasma 3 was Mr Walker's own bike at the time, so it was probably whatever bike was at hand that the wheel fits in.

In the first test against the super 9, the Zipp's skyrocketing drag with yaw >5 degrees doesn't really make sense. That is not how disc wheels typically behave so I am pretty skeptical of that result. It's not how drag on bikes with riders behave with or without a disc wheel, actually.


In the second one, a 0.006 difference in CdA at 0 yaw between disc wheels seems much too large to be believable to me. That's about 6 watts at 45kph at a point where the data for the wheels is likely to be the closest vs other yaw angles. Also, 0.183 CdA makes this rider one of the most aero in the world. That's an awfully impressive CdA...

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Ed O'Malley
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Thanks for that, I also thought the data looked too good to be true.

Regarding the super aero rider, I've heard that the boardman tunnel (where I think they do testing) produces faster results than would be expected else where. However I have no clue if that's true.

It's true that the Boardman tunnel did produce lower numbers than other tunnels. It's the only one where I saw several riders report <.200 cda's.

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Ed O'Malley
www.VeloVetta.com
Founder of VeloVetta Cycling Shoes
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"extraordinary claims require extraordinary proof"

What would the reason for that be? Also reading all comments is it still fair to assume there is not much difference between the different disc wheels? Is there much difference between a disc wheel and say a 800 rear deep section wheel? Sorry if those questions have all bee answered already but those are questions that were on my mind for a while and I was hoping to get some "generic" quick answers (if that's even possible).

A large part of it is there's no spokes in a disc wheel that are exposed. So you don't have lot of small bodies cutting up the air. For full disc wheels you also don't have them rotating and wasting more energy that way. But almost no test measures power to rotate.

Lol yes, 300 grams???? My original thought was that Hambini was pimping for Revolver in addition to Winspace.

It would appear though that these guys actually test, so some very odd numbers as you go out to yaw.

Maurice

My opinion, based on no data at all and a little knowledge, is that the trailing edge aerodynamics matter (leading edge less so if it is shrouded by a seat tube) and the different inside and outside widths of the rims make them more or less aerodynamic when paired to specific tires. So you want a disc wheel that will adhere to the "105% rule" with your preferred tire. That is, you want the width of the rim (where you would have a brake track if it was a rim brake wheel) to be 105% of the width of the tire WHEN MOUNTED ON THAT WHEEL. Not the number printed on the side of the tire. So that means getting out some calipers and measuring. Next most important things in the order I personally put them is: number of tires that are compatible (some hookless rims have many tires you can't safely use), quality/durability, weight, bearings.

Edit: I would probably put price just in front of weight on my list.

Edit 2: Flo's published difference between an 90mm deep rear and a disc is about 18g at 0 yaw and 50 grams at 15 degrees yaw. With their 60mm wheel at 15 degrees yaw that goes up to about 110 grams. Similar at 0. So... Is that worth $1200 to $2700? Personal decision of course.

Edit 3: One reason that the Boardman tunnel gave lower drag numbers is that they subtracted the drag that they estimated came from the fixture that holds the bike while other tunnels don't. I think it is better not to subtract it because it very well may be different with different bikes/riders and you don't know for sure exactly what to subtract. There may be other reasons too.

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Ed O'Malley
www.VeloVetta.com
Founder of VeloVetta Cycling Shoes
Instagram • Facebook

I tend to trust the AeroCoach data much more. They do a ton of development work and report modest improvements that are more in line with what you would expect.


https://www.aero-coach.co.uk/store/AeroCoach-AEOX%C2%AE-ULTRA-carbon-road-disc-wheel-p201821567

I would agree, and also tend to trust companies which also do “generalist” testing. Flo with tire aero data, aero coach with some of his stuff (bottles etc), Silca with some of their tire pressure stuff, Jim with some open info on helmets/aero etc, etc.

Maurice

One other thing to consider is Revolver sources a LOT of their "designs" from open moulds... doesn't take too much searching to find them.

Not saying the ASYMM is (I haven't looked) just that a fair amount of their marketing is...not misleading...but definitely broadly hyped.

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My Blog - http://leegoocrap.blogspot.com

Do you have a link to some of those? I’m curious to see and maybe buy.

I'm sorry, it's been a while since I looked. Searching Alibaba for carbon tt wheels should bring up exhaustive amounts, shouldn't be too hard to suss out many of them by pictures. Brake track, flat/lenticular/etc are good things to look for. (for similarities) As always when buying from such sources, it's best to avoid low rep / new sellers and stick to the "big" guys.

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My Blog - http://leegoocrap.blogspot.com

I couldn't find Revolver's exact wheel design on Aliexpress. To be fair, it is a bit unique with its, well, asymmetric design. There are some nice looking ones for ~$600 though.

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Benjamin Deal - Professional - Instagram - TriRig - Lodi Cyclery
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I think the test rider is Harry Walker. He's a long time tt rider and has experimented with the Obree tuck and superman position so I'll guess that his cda is pretty good.
As for the disc drag? Seems too good to be true but we'll priced.

If those tests were done in a windtunnel: you can't test wheels in a windtunnel.

Is that because it doesn’t capture power spin? but most manufacturer tests of wheels are in windtunnels

There are two big differences between discs and deep section wheel and its the combination of those drive the use of discs. Along the same lines all discs (and even disc covers) have these two advantages which is why you don't expect big differences between discs.

In terms of straight line speed discs are faster than any other deep section design because they have a low 'watts to spin'. This is the drag caused by the spokes moving through the air. Watts to spin is also why tri-spoke wheels are very fast. This is not something you can measure in a wind tunnel and so its hard to quantify on charts but is very real.

The other very real benefit of discs is the fact that in the real world they won't ever stall out aerodynamically. This is a fancy way of saying they handle in a very predictable and stable manner and in cross wind situation they are noticeably superior to deep section wheels. Under extreme conditions the stability of discs is a potential problem because it means they are very determined to consistently blow you off course. Kona is the one case where there this occurs with sufficient regularity to ban the use of disc but the general consensus is that disc make bikes easier to handle.

Indeed, the scales of a windtunnel do not measure the vertical components of the rotational drag.
And that fact is already known for many years.
The fact that most manufacturers still test wheels in windtunnel seems indeed silly against this background.

There are multiple ways to measure rotational drag in a wind tunnel. One approach can be seen here https://www.swissside.com/...g-insights?locale=en

It looks like AeroCoach actually did the aero testing for Revolver - if you look here you can see a pic with Xav from AC, and the Revolver data slides are presented in the exact same format that AC use in their slides...

Aerodynamic Performance Data - Revolver - High Performance Cycling Wheels and Aero Equipment for Cycling and Triathlon (revolverwheels.co.uk)