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Discussion Starter · #1 ·
So. I may be buying new wheels, and I wonder: is a deeper wheel more aero than a shallower one? If I bought just any 45mm deep wheel, would it necessarily be more aero than just any 25mm deep wheel?

I don't have the money for the bling brands who publish their wind tunnel results, and I haven't found data for the wheels in my price range, like the Vision Team 35s, for example. Could I be fooled into thinking a wheel is aero or not based only on its depth?
 

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So. I may be buying new wheels, and I wonder: is a deeper wheel more aero than a shallower one? If I bought just any 45mm deep wheel, would it necessarily be more aero than just any 25mm deep wheel?

I don't have the money for the bling brands who publish their wind tunnel results, and I haven't found data for the wheels in my price range, like the Vision Team 35s, for example. Could I be fooled into thinking a wheel is aero or not based only on its depth?
You could but you shouldn't. Depth needs profile to make for aero
 

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Your hunch is correct.

Depth does not equal aerodynamic value.

The shape has tons to do with it, the money and time they spent in the tunnel was worth it.

Are there cheap wheels out there with solid aerodynamic profiles? Sure, you have to look for them though.

If you want something 35mm or less, you're best sticking with the newest alloy designs. Something like the new AL33 rims make a strong argument for themselves. For carbon deeper than that, the profile means quite a bit. It's not just pure aerodynamics, it's also stability in cross winds.

Used to be that rule of thumb was something U shaped instead of V shaped, but that's changed recently. Things aren't that straight forward. A new rule of thumb that's stuck quite well is that wider is better. Internal width for a clincher that's 19mm or more is becoming ideal quite quickly with 25 or 28mm tires. Some fancy pants companies like Zipp are still lagging behind with around 17mm internal widths. Some wheels like the new disc wheels coming out are going over 21mm internal. Ignore external width measurements, they're largely irrelevant. Now a days the widest external point of the rim is usually half way down the section or so, quite a ways away from any relevance to the tire.
 

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Head over to November Bicycles latest blog post and check out some data on the Zipp 303 versus some aluminum rims.

Sent from my Nexus 5X using Tapatalk
 

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the money and time they spent in the tunnel was worth it.
I doubt that conditions in a wind tunnel have much in common with riding on the open road outside.
From a business point of view the money and time may be well spent, if your wheels are on top in a wind tunnel (not road) aero contest and if you find enough buyers who believe that this has any relevance.

If you want aero for the road, get a wheel with as few spokes as possible while still supporting your weight, power and riding style.
If that takes a deep rim, so be it.
I wouldn't worry about shapes.
 

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I doubt that conditions in a wind tunnel have much in common with riding on the open road outside.
Because they use some special air in the tunnel different from what's outside? Believe it or not, but after more than a hundred years of study, the scientists and engineers have some idea what they're doing. Ever flown in an airplane? But of course you have your opinions.
 

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I doubt that conditions in a wind tunnel have much in common with riding on the open road outside.
From a business point of view the money and time may be well spent, if your wheels are on top in a wind tunnel (not road) aero contest and if you find enough buyers who believe that this has any relevance.

If you want aero for the road, get a wheel with as few spokes as possible while still supporting your weight, power and riding style.
If that takes a deep rim, so be it.
I wouldn't worry about shapes.

Ahahaha, you're hilarious.

You and your box section open pro rims with 12 and 14 spokes can come at me anytime bro.

Data is data. You're arguing that gathering the data is only good if a company can spin it to use it as a marketing tool. My comment had nothing to do from a business point of view and had nothing to do with companies putting spin on their marketing to make the data look like something it's not.

And your argument that a wind tunnel and the road are separate from each other is also hilarious. As if the world makes magical wind that's real and a wind tunnel makes fake wind...

So by your standards an AL33 wheel with 24 cx-ray spokes is no more efficient than an open pro rim with 14 round spokes, as long as both can hold the weight, power and riding style of the rider. Or maybe you'll need a "deep" rim for whatever reason, whatever it takes to lower the spoke count right?

Let me guess... you think that wearing a baggy shirt is no worse than wearing a skinsuit right? If there's any difference you couldn't even measure it right?

I think the problem here is that you don't have a clue what you're talking about, you refuse to take the time to learn anything, so you just form some half-assed assumption and go with it as fact. The real problem is that you're passing that assumption on to others now as advice. That's how things like religion start.
 

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I would be interested to know what your forward 'air speed' has to be for the aerodynamic benefits to out weigh the additional weight of the deeper/fatter wheel.

The faster you are going the more benefit you'll get. Long descents ? sure!. Long slow climbs? Not so much.

The type of rides and the speed you are moving is probably going to have a significant effect on the 'value' of your deep section wheels.
 

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Yes, in the november bicycles blog wind tunnel test all wheels are pretty close together at the most common AOAs, despite their different profiles.
So I really wonder why the effort and what it is to the average cyclist.
 

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Discussion Starter · #15 ·
Your hunch is correct.

Depth does not equal aerodynamic value.
...
Thanks for confirming my hunch. I thought there might be more to aero than depth.
And to bwbishop and Roland44: thanks for pointing me to the blog. It's good reading.

The next question, then, is how does one determine aeroness without (ideally) third-party wind tunnel data? Like if I find a bangin' deal on some 40mm wheels that look all deep and semi-toroidal, can I assume they are? Or should I just buy from brands with published data?
 

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Using a tunnel to test for real world conditions when it really matters by those who know what they're talking about. Or maybe they're just practicing voodoo, what do I know.


As for comparing similar depth and shape wheels, well you really would need some sort of third party data and you'd have to trust their numbers.

In reality, similar depth and shape will produce similar numbers with all else being equal. The thing is that all else isn't equal between wheels, and maybe that's where more focus should lie.

The inner width (tire bead width) makes a real world difference. It changes the shape of the tire, the contact patch of the tire, you can really feel it. A "28mm wide x 45mm deep" wheel and a "23mm wide x 45mm deep" wheel of similar shape and characteristics with the same tires will not perform the same. Aerodynamics of the rims aside, the tires won't perform the same, they won't feel the same either.

Another consideration that I value personally is cross wind resistance or whatever you might call it. Maybe cross wind stability. You know the crazy new Zipp 454 NSWs? The ones that look like saw blades? They aren't any more aerodynamic than the regular shape ones, certainly nothing they can market or boast about anyway. The aerodynamics actually play zero role in that new design, it's all about cross wind stability. The big claim is that that weird whale inspired shape is there to increase stability, that's pretty much it. So it's really only relevant for the front wheel, but hey, they need to sell stuff.

So the 454 and the 404 have basically identical profiles and depths, also they perform the same aerodynamically. So it's a good example how another factor, cross wind stability, will make a better wheel. Keep in mind though that it's different for each person. The more you weigh, the less it matters usually. And there's usually a certain depth that people will draw the line at for a certain wind speed. Such as nothing over 50mm deep if the wind is 25mph sustained or higher as an example. Everyone has their own limits and values based on their fit, weight distribution, weight, level of risk acceptability, etc.

So really, you need to decide what's most important to you. I haven't even mentioned braking performance yet... and not even talking disc brakes, braking with rim brakes on carbon wheels varies tremendously by brand. It seems as though each brand has their own way of handling the problem, they are quite varied and different. Also all of the different pads used is crazy. Some work very differently from others. Braking is a big consideration for those in the mountains and hilly places.

Also hubs and spokes and build quality and reputation for brake rub or stiffness or... there's so much.

TLDR: There's a lot to buying wheels, much more than depth and shape really. You need to prioritize what's most important to you and read a lot of reviews to find out what makes the wheels all so different so you can choose the right one for you.
 

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Discussion Starter · #17 ·
Thanks for the detailed answers, MMs. I know there's a lot to consider in wheels, like the braking you mentioned. I've heard that carbon can be squeaky, and that would drive me nuts. So I'm leaning towards something as aero as shallower aluminum can get; a balance of reasonable weight, good and quiet braking, and reasonable cost. So those November offerings may be the ticket.
 

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Thanks for the detailed answers, MMs. I know there's a lot to consider in wheels, like the braking you mentioned. I've heard that carbon can be squeaky, and that would drive me nuts. So I'm leaning towards something as aero as shallower aluminum can get; a balance of reasonable weight, good and quiet braking, and reasonable cost. So those November offerings may be the ticket.
For sure. Those new AL33's in a build from them would be fantastic.

But back to carbon real quick:

Enve today released a new 3.4 wheelset. This version is actually less aerodynamic than the previous version. Simon Smart just made a statement in the release that I think backs me up, let me share it.

Simon Smart said:
Drag reduction is only one part of the equation. In order to make a fast wheel, attributes such as stability, rolling resistance, shape of the tire bed, and the construction of the rim itself must be carefully considered to produce maximum efficiency on the road. The new SES 3.4 carefully balances all these attributes for a net gain in efficiency over other wheelsets in this category.
And let me elaborate a little bit on that with a video about shapes from my favorite wheel brand:


And just a quick note from Simon's quote. The "construction of the rim itself" is what I want to make a quick point about. Knight is the ONLY wheel company in the world building carbon wheels without traditional bladder techniques, they use the EPS mold technique. Just one more reason they're my favorite but the list is long.
 

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This is the best quick overview of aero effects I've ever seen. Everyone should read it twice, slowly, if they are considering aero wheels.

Also ask yourself the question - what is YOUR honest "average" speed, and how important are aero effects at THAT speed.

The rim/tire influence over watts required at 30 MPH drops by the cube of the speed when you go slower. This is because the drag force (F) is proportional to the square of the speed, and the watts proportional the aero drag force times velocity (W = F * V).
This means that 3W savings at 30 MPH for most common conditions translates to
1.7 W 25 MPH
0.9 W 20 MPH
0.6 W 18 MPH
0.4 W 15 MPH

If your average speed is more in the range of 15-20 MPH, notice that latex tubes and better tires are going to give you a much larger watts savings that aero wheels, as pointed out in the article above.
 
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