It turns out the Campy Boras are actually quite aero (Tour Magazine latest aero hoops test)

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ichobi
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by ichobi

The watts difference did raise some doubt compared to previous tests we have seen floating around from manufactures and some other magazines. Part of this might be because the result is an average drag from various yaw angles. So the difference are minimal at best. Also note that it's tested with spinning dummy legs.

If you look at graphs that show drag from each yaw (not averaged). The difference tend to be more drastic.

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Look at this Flo's test

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The difference between Open Pro and Flow 60 is almost whopping 250 grams at 15 degree! Even then, the difference between Flow 30 and 60 - still comes out more 40-50g from 10 degree onwards. A lot more than averaged drag shown in Tour result delta. (202 vs 404) for example.

And here's from Trek whitepaper on their Aeolus wheel test.
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by Weenie


ultyguy
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by ultyguy

Precisely, I figured 0 yaw was probably weighted a lot.

Not to dive into the weight/aero debate etc. but just think about where the big splits are really made in your races/events. Is it when you're going 20kph up an 8% gradient or 50kph in a crosswind or maybe even on a descent....that should drive your choice.
Last edited by ultyguy on Tue Aug 09, 2016 4:56 pm, edited 1 time in total.

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kgt
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by kgt

I don't think Tour's test tell the absolute truth (far from that IMO) but I would trust them much more in comparison to any test coming from a manufacturer.

ichobi
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by ichobi

If you think about it, Tour's test actually turns the table on aero wheels testing unlike any data we have seen before. With the difference between wheels so minimal. Prior to this who would have thougnt a DuraAce C35 with their 15mm internal width would be as aero as any torodia rims at all? Don't know if their procedure can mimick real life riding, but thats probably as close as you can get in a tunnel environment. And yes, Zero yaw must weight a lot.

This is how they test for those who didn't buy the mag.
ImageImage

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helldiver
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by helldiver

So according to this test, the weighted average difference between Zipp 404 (222W) and Shimano C24 (239W) is 17W and this is small ? C24 with the low (bladed) spoke count and quite rounded rim is still massively more aero then old box section rim wheel with 32/36 spokes (which is very often used as a "standard" reference wheel in manufacturer comparisions, despite almost nobody using them anymore), so I'm not surprised at all that the difference between them and medium (58mm) depth carbon wheels is "only" 17W. In fact 17W is quite a lot, try to raise your threshold by 17W, it's not easy at all, it takes some serious training. What did you expect, that slapping 404 Zipps instead of the modern shallow aluminium OEM wheels on your bike will gain you 50 free watts at speed ? :mrgreen:

pdlpsher1
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by pdlpsher1

Anyone who has used a wattmeter knows that 5-10 watts difference averaged over the entire ride is huge. Put differently, on the same ride that I do a difference in average speed of 0.2-0.3mph is huge, probably a difference in average power of 5-10 watts over the entire ride. So a 'free' speed gain of 0.2-0.3mph is well worth it.


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pdlpsher1
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by pdlpsher1

The irony of deep vs shallow wheels is that the slower you go the more benefit one will gain from a deeper wheel. Various tests have proven that deeper wheels have a huge advantage over shallow wheels when the yaw angle is high. This is due to the sail effect which results in a negative drag value at high yaw angles. At 28mph chances are the average yaw angle will be extremely small. A slower rider will see much higher average yaw angles. So on a time trial race the aero difference will be quite small between a shallow and a deep rim. For the mortals a deep wheel will give you much greater advantage. I would love to see the test done at 20mph vs 28mph.


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ichobi
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by ichobi

When i said small difference, I think more about the 35 vs 50 vs 58 depth in the test. Like old school da c35 (228w) vs 404 (222w). 6 watts arent all that much given all the marketing we all led to believe. If you compare to a c24 surely you will be missing out some free speed. Thats 34mm of rim height difference.

Same goes for Bora 35 and 50mm. (226 vs 224 watts). I thought the difference would be more stark between 35mm and 50mm rim prior to reading this test.


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dunMisk
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by dunMisk

Put this in here as well:

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According to Flo: 80% of the riding is in between 0 and 10 degrees. Most aero advantage of deep wheels is beyond 10 degrees. Even for their own wheels. They are quite honest about it.

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WMW
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by WMW

ichobi wrote:When i said small difference, I think more about the 35 vs 50 vs 58 depth in the test. Like old school da c35 (228w) vs 404 (222w). 6 watts arent all that much given all the marketing we all led to believe.


If the total drag for a leg dummy on a bike is 222-228W then 6 watts seems like a lot to me. What was the speed?

I've been saying forever that if you get a nicely shaped 25+mm rim with minimal aero spokes then you have an aero wheelset. The gains for going deeper are tiny until you get out to higher yaw, where you will probably be wishing you had shallow rims anyway.

Really hate how aero drag always gets reported in grams and watts, usually with no speed given. Speed makes a huge difference! 10W at 20mph is 3.4x 10W at 30mph! Even if the speed is given it always "ok how do I relate this to my riding speed"? It's a mess every time. Start using CdA for gawd's sake!
formerly rruff...

DamonRinard
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by DamonRinard

Many of us know differences are biggest beyond ten degrees yaw. So it might be interesting to see this article: Real World Yaw Angles

http://www.slowtwitch.com/Tech/Real_Wor ... _5844.html

Written by Dr. Nathan Barry, aero design engineer in the road group at Cannondale Bicycles. He has a PhD in cycling aerodynamics from Monash University in Australia and his research can be found in multiple peer-reviewed publications. Nathan has been racing triathlons for 15 years in everything from ITU to half ironman and off-road multisport.
Damon Rinard
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Cycling Sports Group, Cannondale
Ex-Kestrel, ex-Velomax, ex-Trek, ex-Cervelo

ichobi
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by ichobi

@WMW it's 45kph. Protocol are posted a few posta above.

@DamonRinard thanks for the link!


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Stueys
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by Stueys

dunMisk wrote:I read bought and read the article as wel. I'm quite surprised how little the actual aero effects are. I mean the whole range is from 222 to 239 watts at 45kph. And if you take out the very obvious non-aero wheelsets (C24 / Ksyrium / Hyperion), the difference is only 8 watts between the fastest and the slowest. If I had to conclude from this test, if your going with a decent 30+ mm alu rim and stiff wheel/hub/spoke combination, your set. The difference will only about 4 watts. Spend the rest of your money on spinningclasses / eating well / snug fitting clothes (excluding an aero frameset ofcourse).


Guess it depends on your expectations, Id be pleased to add 17w to my ftp over a hard summers training season.

As you say the delta between the top aero wheels is interesting, maybe this is why the marketing push is now on braking performance? Everyone has broadly caught up on the right aero shaping and its playing in the margins now.

dunMisk
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by dunMisk

DamonRinard wrote:Many of us know differences are biggest beyond ten degrees yaw. So it might be interesting to see this article: Real World Yaw Angles

http://www.slowtwitch.com/Tech/Real_Wor ... _5844.html

Written by Dr. Nathan Barry, aero design engineer in the road group at Cannondale Bicycles. He has a PhD in cycling aerodynamics from Monash University in Australia and his research can be found in multiple peer-reviewed publications. Nathan has been racing triathlons for 15 years in everything from ITU to half ironman and off-road multisport.


Good stuff. Especially the graphs that show the faster your ride, the less likely you will be at higher yaw angles.

It makes you think about the olympic tt. They average 45 kph, even with the climbs. They needed braking power for the dangerous descents (damn, spartacus was fast). How would the time be different if someone rode a medium-high alu rim up front, just for the braking? (I know, I'm skipping tyre grip, and there aren't any medium-high alu tubular rims available for as far as I know).

Marin
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by Marin

They wouldn't be any faster on an aluminum rim.

by Weenie


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