The conventional wisdom has been that there shouldn’t be large drag differences between various rear disc wheels with Aerocoach claiming a ~2 watt difference between them and the Hed Jets at 45 kph.
However Revolver is claiming HUGE differences between the Zipp Super 9/HED Jet and their asymmetrical design. These gains seem huge does anyone else have any info confirming or contradicting this?
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.
The conventional wisdom has been that there shouldn’t be large drag differences between various rear disc wheels with Aerocoach claiming a ~2 watt difference between them and the Hed Jets at 45 kph.
However Revolver is claiming HUGE differences between the Zipp Super 9/HED Jet and their asymmetrical design. These gains seem huge does anyone else have any info confirming or contradicting this?
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…
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.
“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.
“extraordinary claims require extraordinary proof”
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
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).
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.
“extraordinary claims require extraordinary proof”
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
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®-ULTRA-carbon-road-disc-wheel-p201821567
“extraordinary claims require extraordinary proof”
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
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®-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.
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.
Do you have a link to some of those? I’m curious to see and maybe buy.
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.
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.
The conventional wisdom has been that there shouldn’t be large drag differences between various rear disc wheels with Aerocoach claiming a ~2 watt difference between them and the Hed Jets at 45 kph.
However Revolver is claiming HUGE differences between the Zipp Super 9/HED Jet and their asymmetrical design. These gains seem huge does anyone else have any info confirming or contradicting this?
If those tests were done in a windtunnel: you can’t test wheels in a windtunnel.