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PostPosted: Sat Sep 23, 2017 10:34 pm 
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http://www.tour-magazin.de/komponenten/laufraeder/laufrad-test-fuer-rennraeder-mit-scheibenbremsen/a45092.html

too bad tour mag has stopped publishing the english edition. looking at the aero data the 3t discus is the best. there is not plot points for a non-aero control wheelset. did anyone in germany buy this issue. curious what is the aero penalty vs traditional rim wheelsets

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PostPosted: Tue Oct 03, 2017 4:07 pm 
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Can someone explain to me how significant these differences actually are? Like 0.16 vs. 0.17 at very extreme angles, so significant is this anyway?


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Posted: Tue Oct 03, 2017 4:07 pm 


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PostPosted: Tue Oct 03, 2017 5:02 pm 
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What I take from those graphs is that there is very little difference between any of those wheels for the average road cyclist. The vast majority of yaw angles experienced by cyclists is under 10%. Only if you are on the Kona ironman course are you really needing to think about wheels that perform well at 12 or 15 degrees.

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

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PostPosted: Wed Oct 04, 2017 10:22 am 
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spartan wrote:
looking at the aero data the 3t discus is the best.

And it's also a 60mm wheelset whereas most of the wheels tested from the other premium manufacturers were between 40 to 50, so you'd hope it was fast. Otherwise it looks like what was already mentioned - pretty much everything is pretty damn close these days.


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PostPosted: Wed Oct 04, 2017 12:10 pm 
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L3X wrote:
Can someone explain to me how significant these differences actually are? Like 0.16 vs. 0.17 at very extreme angles, so significant is this anyway?


Real world yaw angles will be 0 to 5° unless you are going very slow or are riding in the desert or on the seashore.

In track aero tests, shallow wheels perform very well, and the biggest difference is in tire width.


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PostPosted: Wed Oct 04, 2017 8:17 pm 
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Location: Edinburgh, Scotland
Beaver wrote:
Here are the Zipp results of the last rim brake test:

Image



I don't know if i'm reading the graph correctly but do these results show that a 202 rim will be as fast as a 404 or 303 in 0 degrees yaw, and actually faster at higher yaw angles?
Seems like a no-brainer on which wheels are best.


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PostPosted: Wed Oct 04, 2017 9:08 pm 
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cwA is drag, so less drag is better


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PostPosted: Wed Oct 04, 2017 9:13 pm 
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It shows that 202 are as fast as 303 and 404 at 0 to 8 degrees yaw. We know that 202s are lighter too...

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PostPosted: Mon Oct 23, 2017 8:49 am 
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But don't expect to notice these small one digit watt differences at 45kmph on the road. ;)

I can only recommend using 21C rims with 23 or 25mm tires and heavily reduced pressure. On rough tarmac you will notice a real difference here. ;)

Image

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PostPosted: Mon Oct 23, 2017 11:02 am 
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Thanks Beaver! Where is this graph from?
I find interesting that it totally busts the myth that testing tires on a roller in a lab is valid. It also gives us a clue why high tpi tubulars and open tubulars, which are more flexible, posiibly have a lower crr because of that. It finally confirms our empirical knowledge that a pressure around 90-100 psi is the best for most conditions.

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PostPosted: Mon Oct 23, 2017 1:07 pm 
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kgt wrote:
Thanks Beaver! Where is this graph from?
I find interesting that it totally busts the myth that testing tires on a roller in a lab is valid. It also gives us a clue why high tpi tubulars and open tubulars, which are more flexible, posiibly have a lower crr because of that. It finally confirms our empirical knowledge that a pressure around 90-100 psi is the best for most conditions.


Given you don't know where it's from aren't your definitive statements re "totally busting myths", "finally confirms" etc somewhat premature? :D

Nonetheless it looks intuitively sensible. 90-110psi depending on road conditions, for a c75kg rider is right IME

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PostPosted: Mon Oct 23, 2017 1:12 pm 
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sawyer wrote:
kgt wrote:
Thanks Beaver! Where is this graph from?
I find interesting that it totally busts the myth that testing tires on a roller in a lab is valid. It also gives us a clue why high tpi tubulars and open tubulars, which are more flexible, posiibly have a lower crr because of that. It finally confirms our empirical knowledge that a pressure around 90-100 psi is the best for most conditions.


Given you don't know where it's from aren't your definitive statements re "totally busting myths", "finally confirms" etc somewhat premature? :D

Nonetheless it looks intuitively sensible. 90-110psi depending on road conditions, for a c75kg rider is right IME


It confirms whatever an engineer should already know so... ;)

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PostPosted: Mon Oct 23, 2017 2:03 pm 
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https://silca.cc/blogs/journal/part-4b- ... -impedance

I never noticed any big differences between wheels until I got 21mm inner width. When you ride on smooth asphalt and then get on rough tarmac with a 23mm tire on a 17C rim with 100psi you will notice an immediate increase in rolling resistance and probably change to a lower gear. With a 25mm tire on 21C with 60psi not so. And it doesn't feel slower on smooth asphalt either...

With aero wheels you notice a slight improvement when the wind comes from diagonally forward or descends at high speeds. But in all other cases... :noidea:

You need to be really fast to notice it. Wider rims help everybody.

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PostPosted: Mon Oct 23, 2017 7:06 pm 
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kgt wrote:
Thanks Beaver! Where is this graph from?
I find interesting that it totally busts the myth that testing tires on a roller in a lab is valid. It also gives us a clue why high tpi tubulars and open tubulars, which are more flexible, posiibly have a lower crr because of that. It finally confirms our empirical knowledge that a pressure around 90-100 psi is the best for most conditions.


This only holds true for tire pressure (i.e. you can't keep increasing tire pressure to lower crr), not the rolling resistance of the tires themselves. The relative ranking of tires tested in the real world would still track the results of the roller tests because the primary drivers of energy loss is still going to be the same (e.g. hysteresis). So yes, tires with more flexible casings will perform better on the road, but they also performed better on rollers anyways (the top tires are usually supple casings, thin tread, little/no puncture protection).

So just like wind tunnel tests, you have to understand the results of rolling resistance tests in the context that they're done under specific conditions and how they apply to the real world is something you'd have to test on your own, for your own conditions.

Marin wrote:
L3X wrote:
Can someone explain to me how significant these differences actually are? Like 0.16 vs. 0.17 at very extreme angles, so significant is this anyway?


Real world yaw angles will be 0 to 5° unless you are going very slow or are riding in the desert or on the seashore.

In track aero tests, shallow wheels perform very well, and the biggest difference is in tire width.


Yup, looking at Mavic's data, you can see that you'll find a lot more wind near the coast (Kona) than inland (Annecy). Sec. 3:
http://engineerstalk.mavic.com/en/yaw-a ... an-course/

So where you ride is also going to factor in the relative performance of wheels.

And of course no aero thread is complete without the aero rule of thumb, especially when the data is presented in CdA (yay!)
0.1 lbs (50 g) of drag (@ 30 mph) = 0.5 s/km = 5W = 0.005 m^2 CdA = 0.0005 Crr


These results would be a lot more interesting if they included rotational drag, especially compared to some of their non-disc counterparts :noidea:


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PostPosted: Mon Oct 23, 2017 9:36 pm 
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It would be even more interesting when included data measured at "real life speed" ; like 35-40 kph range. But it rather won't happened. Wheel manufacturers don't allow for such heresy ;)

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Posted: Mon Oct 23, 2017 9:36 pm 


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