# Aero difference between 35mm and 50mm



## Wesquire (May 27, 2015)

Anyone have any data on a comparison like this? I'd like to know how much difference each 10mm makes and where the diminishing returns get significant


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## steelbikerider (Feb 7, 2005)

This should answer your questions.
November Bicycles: Race smart. - November Bicycles Blog
go down to the August 4 entry. 
The November blogs have a lot of objective and subjective information on have wind tunnel testing, stiffness data on rims, spoke counts, tire width, frames, building with carbon and more.


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## MMsRepBike (Apr 1, 2014)

Shape has more to do with it than depth in many cases.


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## jfaas (Jan 31, 2014)

MMsRepBike said:


> Shape has more to do with it than depth in many cases.


This, you will see accounts where the interface of the tire and rim or the smoothness of the brake tracks has a significant effect on the aerodynamics.


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## coachboyd (Jan 13, 2008)

It definitely depends on shape of the wheel. We were just in the wind tunnel two days ago for four hours and found out all sorts of things.

Shape mainly affects the aero qualities at higher crosswind angles (yaw angles), and we saw 44mm wheels that outperformed 58mm wheels at every yaw angle above 5 degrees.

In general, the deeper you go, the more aero once you start introducing a little bit of crosswinds. However, this is also where tire selection, tire size, and rim shape really start to affect the aerodynamics.


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## Notvintage (May 19, 2013)

MMsRepBike said:


> Shape has more to do with it than depth in many cases.


True dat. The Zipp 202 is only 30mm but is more aero than many 50mm wheels.


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## ziscwg (Apr 19, 2010)

coachboyd said:


> It definitely depends on shape of the wheel. We were just in the wind tunnel two days ago for four hours and found out all sorts of things.
> 
> Shape mainly affects the aero qualities at higher crosswind angles (yaw angles), and we saw 44mm wheels that outperformed 58mm wheels at every yaw angle above 5 degrees.
> 
> In general, the deeper you go, the more aero once you start introducing a little bit of crosswinds. However, this is also where tire selection, tire size, and rim shape really start to affect the aerodynamics.


Well, I hope your Altamont rims are nice and aero. I'm going to build my next set with them. I like mtns and DH, so I stick the Al rims for now.


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## Roland44 (Mar 21, 2013)

jfaas said:


> This, you will see accounts where the interface of the tire and rim or the smoothness of the brake tracks has a significant effect on the aerodynamics.


Exactly..


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## B05 (Jul 31, 2011)

coachboyd said:


> It definitely depends on shape of the wheel. We were just in the wind tunnel two days ago for four hours and found out all sorts of things.
> 
> Shape mainly affects the aero qualities at higher crosswind angles (yaw angles), and we saw 44mm wheels that outperformed 58mm wheels at every yaw angle above 5 degrees.
> 
> In general, the deeper you go, the more aero once you start introducing a little bit of crosswinds. However, this is also where tire selection, tire size, and rim shape really start to affect the aerodynamics.


admittedly I'm too sleepy to research on anything now, but what would be "faster" on varying wind conditions from these choices:

21mm tires, 23mm width rims
23mm tires, 23mm width rims
25mm tires, 23mm width rims

I have no idea if you should match the width of your rim with your tires. These tires expand 2-3mm when you inflate them as well. I'm not scientifically sound like you but I'd love to get a for "dummies" answer.

EDIT:

that Novemberbicycles link actually answered my question. thanks :thumbsup:


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## Wesquire (May 27, 2015)

I'm assuming between two of the same profiles. Say Zipp 303 vs 404. How much difference?


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## coachboyd (Jan 13, 2008)

Just actually tested that the other day (along with our 44 and 60 stuff we're working on)
Zipp 303 is 45mm deep
Zipp 404 is 60mm deep
Our 44 is 44mm deep
Our 60 is. . .why yes, you did guess correctly. . .60mm deep\

All testing was done in same tunnel with same tire (23mm Conti GP4000 set to 100PSI)
reds are Zipp, blues are us

At very light winds there's not much difference between most wheels. However, as you start getting more and more crosswinds, that is where the difference between wheels (and depths) really starts to be noticeable.


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## SauronHimself (Nov 21, 2012)

coachboyd said:


> Just actually tested that the other day (along with our 44 and 60 stuff we're working on)
> Zipp 303 is 45mm deep
> Zipp 404 is 60mm deep
> Our 44 is 44mm deep
> ...


I hope Zipp sees this. They're starting to lag in terms of both performance and price point.


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## ziscwg (Apr 19, 2010)

SauronHimself said:


> I hope Zipp sees this. They're starting to lag in terms of both performance and price point.


they have always lagged in price point...........

You'd think with that kind of price point, their hubs would be perfect and last for ever.


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## berserk87 (Jul 24, 2014)

coachboyd said:


> Just actually tested that the other day (along with our 44 and 60 stuff we're working on)
> Zipp 303 is 45mm deep
> Zipp 404 is 60mm deep
> Our 44 is 44mm deep
> ...


Hi - I am having the dumbs today - can you explain what units of measure are being used on the X and Y axes on this graph?


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## coachboyd (Jan 13, 2008)

berserk87 said:


> Hi - I am having the dumbs today - can you explain what units of measure are being used on the X and Y axes on this graph?


Sure,

Left side is the grams of drag. Lower means more aerodynamic.
Bottom is the yaw angle, it's the angle the wind is hitting the wheel. A higher yaw angle represents more of a crosswind.

If you are riding on a calm day in terms of wind, you are likely seeing 0-5 degrees yaw angle. If it's a windier day and you have the wind coming from your side, you are seeing a higher yaw angle. Depending on your speed, the wind speed, your direction, and the wind direction will all influence what the actual yaw angle on the wheel would be.


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## skinewmexico (Apr 19, 2010)

What is this? A wind tunnel chart without showing wheels compared to a Mavic Open Pro? Heresy! Just kidding, coachboyd, thanks for sharing. I just always find the Open Pro thing funny.


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## cnardone (Jun 28, 2014)

coachboyd said:


>


OK, so what does this mean in practical terms? how much time savings does your 60 have over your 44. Understanding that no ride is the same, wind conditions, rider, etc... Say over a 40K time trial at an ave speed of 33kph?


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## Wesquire (May 27, 2015)

I'd like to see a comparison to the chinese carbon wheels as well. They are becoming so popular, you'd think companies like Zipp would demonstrate their superiority if it were overwhelming.


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## Dunbar (Aug 8, 2010)

Wesquire said:


> I'd like to see a comparison to the chinese carbon wheels as well. They are becoming so popular, you'd think companies like Zipp would demonstrate their superiority if it were overwhelming.


Most of the newer rims are U shaped which I'm sure the Chinese carbon rims have copied. You are buying build quality and reputation when you buy from an established company, not performance at this point.


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