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PostPosted: Mon Apr 08, 2013 10:44 pm 
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Good memory. Here's results from Tour magazine, which were posted to the BikeTechReview forum. The Michelin Pro 2s were excellent, while the Continental GP 3000s were actually worse than the Gatorskins. These are results from roller tests:

Deda Tre Giro d'Italia......... 0.0038
Vittoria Open Corsa Evo CX....... 0.0039
Michelin Pro 2 Race...........0.0042
Vittoria Diamante Pro Rain....... 0.0044
Michelin Megamium 2...........0.0047
Pariba Revolution............0.0048
*Veloflex Carbon (Tubular)....... 0.0049
Michelin Carbon.............0.0050
*Gommitalia Route du Nord (Tubular)...0.0050
Panaracer Stradius Pro......... 0.0051
Schwalbe Stelvio Plus..........0.0052
*Gommitalia Platinum (Tubular)..... 0.0053
*Vittoria Corsa Evo CX (Tubular).... 0.0054
Schwalbe Stelvio Evolution Front.... 0.0056
Continental GP Force (rear specific).. 0.0057
Hutchinson Fusion............0.0057
Schwalbe Stelvio Evolution Rear.....0.0057
*Vittoria Corsa Evo KS (Tubular).... 0.0057
Continental Ultra GatorSkin.......0.0058
Ritchey Pro Race Slick WCS....... 0.0058
Schwalbe Stelvio............ 0.0059
*Continental Competition (Tubular)... 0.0059
*Veloflex Roubaix (Tubular).......0.0059
*Contintal Podium (Tubular).......0.0060
Specialized S-Works Mondo........0.0061
Continental GP 3000...........0.0067
Hutchinson Top Speed.......... 0.0069
*Schwalbe Stelvio (Tubular).......0.0069
Continental GP Attack (front specific). 0.0073
*Tufo Elite Jet (Tubular)........0.0073
*Schwalbe Montello 300 (Tubular).... 0.0075
*Tufo Hi-Composite Carbon (Tubular)...0.0077

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PostPosted: Tue Apr 09, 2013 1:50 am 
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flow aero test results

http://flocycling.blogspot.ca/2013/04/f ... sults.html

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Posted: Tue Apr 09, 2013 1:50 am 


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PostPosted: Tue Apr 09, 2013 2:51 am 
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djconnel wrote:


Notice that around the 1:30ish mark he walks over to the back wall. I'm guessing that little box on the top of the pendulum is a laser pointer, and he's checking to see when the dot stops moving. Then he looks at his watch, probably to stop his timer.


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PostPosted: Tue Apr 09, 2013 3:29 am 
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Hey dj, I was actually thinking of the "afm" chart, but as I recall his data usually lined up pretty well with that tour set which was one of the first that really seemed to get people talking rolling resistance.

But as the poster above showed with flo's data, this stuff can be moot in light of aerodynamics. Tom a. provided some of the tires to flo, so I think we're likely to see some sort of aero/rolling resistant chart showing at what speeds what tires shine and a combined drag calculation.


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PostPosted: Tue Apr 09, 2013 4:17 am 
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NGMN wrote:
Tom a. provided some of the tires to flo, so I think we're likely to see some sort of aero/rolling resistant chart showing at what speeds what tires shine and a combined drag calculation.


http://bikeblather.blogspot.com/2013/04 ... tters.html


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PostPosted: Tue Apr 09, 2013 5:41 am 
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Thanks al. This is really interesting stuff. One thing that sprang to mind as I was reading was tom's analysis was that we always talk about speed's effect on yaw. I wonder what the speed of the mavic riders who collected the data was. Because if my quick math is right, mavic is saying about 75 percent of yaw is under 10 on either side. That's a fair amount less than some companies have talked about


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PostPosted: Tue Apr 09, 2013 8:00 am 
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djconnel wrote:
I hadn't realized the Corsa CX's were available in 25C. Those, it seems, are the winner here. But more generally that fat tires, even 32mm, can be quite fast.


I think they came out early last year. My new fav!


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PostPosted: Tue Apr 09, 2013 3:44 pm 
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NGMN wrote:
Thanks al. This is really interesting stuff. One thing that sprang to mind as I was reading was tom's analysis was that we always talk about speed's effect on yaw. I wonder what the speed of the mavic riders who collected the data was. Because if my quick math is right, mavic is saying about 75 percent of yaw is under 10 on either side. That's a fair amount less than some companies have talked about


It's in close agreement with my estimates. The key is you need the actual wind speed near the ground, which is considerably less than wind aloft, and is less in inland roads than it is on coastal roads or desert roads with unobstructed wind.

"Some companies" have a vested interest in emphasizing conditions where large yaws are prominent, for example mid-pack age-group triathletes riding the Kona Highway.

Image

Robert's typically minimalist response is as usual directly on target. But the relevant issue here is the difference in wind force @ 30 mph was a few gram-equivalents at low yaw. The BQ test was at around 27 kph. The ratio of wind force for these two speeds is around 31%. So the difference in wind force is around 1 gram-equivalent. A difference in Crr of 0.01% is 8 gram-equivalents for rider + bike = 80 kg. So the wind resistance difference between tires is a significant but relatively small contribution to error in results. I'm more worried about run-to-run variation in wind resistance since they use actual riders and not a Dave Zabriskie dummy (not to be confused with a dummy, Dave Zabriskie. Just kidding.) Also run-to-run variation in wind. I am therefore not taking too seriously the results for a specific tire in that regard.

But once you have Crr, it's an excellent point that in picking the tire wind resistance is a factor of comparable importance, especially when making comparisons between 23 mm and 42 mm tires, as Jan Heine does.

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PostPosted: Tue Apr 09, 2013 8:06 pm 
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Hey Dj, I have seen your estimates, and my two gripes are that you assume that much of yaw is at 0; whereas most thinking is that almost nothing is truly 0, maybe 1-2 but almost never 0. So really, I think what mavic did with the "double hump"(I'm no statistician) was probably a good bet.

Second, I think your graph, and what I was getting at with the Mavic graph, is lacking a rider speed metric. So, I think anytime we have a "yaw distribution" graph, there should really be a correlating rider speed metric. A rider doing 27 mph in a Time trial experiences much lower yaw than a 18mph club rider. For instance, what rider speed did you make your assumptive distribution?

Because really when I think about it, we are talking about rolling resistance versus speed as a result of wheel/tire aerodynamics and how to maximize that equation for different riders.


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PostPosted: Tue Apr 09, 2013 11:58 pm 
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Hi,

Just picking two tyres I know very well.

Quote:
Pariba Revolution............0.0048
*Veloflex Carbon (Tubular)....... 0.0049


Veloflex Carbon is very close to a DedaTre as far as theoretical Crr is concerned. Not sure who makes DedaTre tyres but it could well be Veloflex. All DedaTres are rather heavy but otherwise fine.
Pariba Revolution is a slick clincher with a relatively low TPI count and while a fine tire, nothing special at all.

A Schwalbe Milano with a butyl inner tube and no puncture resistance should be ranked on top and is in fact the best rolling tubular I know of.

Neither the Pariba nor the Milano are no longer produced. Pariba being absorbed by Vredestein, Schwalbe replaced their best tubular by adding an anti-puntcure belt robbing it from its very raison d'etre. And so it goes....

Which begs the question: How big is the impact of an anti-puncture belt (except perhaps for Conti's clever Vectran one, but I'd still like to know) on rolling resistance anyhow?

I figure it's rather massive going by the impact of casings in general.
Ironically, I never punctured a Schwalbe Milano which is less than my puncture count for Veloflex Carbons. The trick is to keep your eyes peeled and avoid urban areas at all cost and age your tyres.
Not so sure which of the two was faster but we're comparing a 25 Euro tub to a 85 Euro one here.

Bottom line is, in order to sell a tyre to fool, you need a foolproof tyre. And vice versa.....

Ciao, ;)

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PostPosted: Wed Apr 10, 2013 1:07 am 
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The double hump is there if the wind speed is constant. But once the wind speed is randomized (assumed independent along two directions) it convolves the double hump into a single hump. If the wind is always from a single direction, for example a coastal road which is constantly hit by cross-winds, the peak would shift from zero. But my analysis assumed random wind speed.

A single hump is a small victory for the Central Limit Theorem, which basically says if you have enough sources of randomization, you get a Gaussian probability distribution (typically).

Here's the Mavic measured data:
Image

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PostPosted: Wed Apr 10, 2013 9:25 am 
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Location: Sweden
djconnel wrote:
The best tires are various out-of-production racing tubulars which are no longer available starting with a Challenge 33-622 tubular @ 0.25%.

The Challange tire is a clincher, a hand glued prototype. Read more about it on page 39 of the magazine (BQ Spring 2013 issue).


Quote:
I hadn't realized the Corsa CX's were available in 25C. Those, it seems, are the winner here. But more generally that fat tires, even 32mm, can be quite fast.

They have been available here in Europe at least since 2010, when I bought mine.
When I did my own RR-test (roll down <15km/h) they cam out on top.
I also like the way they feel. But they don't have much in puncture protection

From 2013 it looks like Vittoria have dropped Evo from the name
and that the Corsa SC is also available in 25mm
http://www.vittoria.com/en/product/cott ... oduct-4472" onclick="window.open(this.href);return false;
But I have no idea of were to buy them.


/Håkan
SWEDEN


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PostPosted: Wed Apr 10, 2013 3:18 pm 
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Thanks!

In the Bicycle Quarterly article, the best tire is listed as "Challenge Prototype hand-glued (33-622 mm) (no longer available)". I'd assumed this was a tubular, since clinchers aren't typically glued.

However, later in the article it is stated:

"The tire with optimal performance would be a clincher with the casing of a traditional tubular tired. The tread would be relative thin, with a fine pattern, and it would be hand-glued to the casing. This tire would be about 40 mm wide so it could be run at relatively low pressures which would improve its rough-road performance. Tires like these used to exist. During the 1940s and 1950s,French randonneurs used handmade clincher tires that offered incredible performance, according to those who have ridden them. The Challenge prototype tires show that such tires indeed offer better performance than any tires available today."

They go on to explain that when the tread went from being hand-glued in prototype form to vulcanized in production form (the Paris-Roubaix) suppleness was lost and rolling resistance increased.

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PostPosted: Wed Apr 10, 2013 5:41 pm 
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Hi,

Quote:
"The tire with optimal performance would be a clincher with the casing of a traditional tubular tired.


Those are often called "Open Tubulars". Challenge still has a 27mm wide one that measures pretty close to 29mm but I understand you'd want even wider ones.
How are these "Grand Bois" tyres made? Vulcanized or glued on?

Ciao, ;)

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PostPosted: Wed Apr 10, 2013 7:01 pm 
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Theres some pretty great graphs from cyclenutnz over on slowtwitch which is starting to get to the point of how complex aerodynamics, rolling resistance and speed is depending on your size and speed:
http://forum.slowtwitch.com/cgi-bin/gfo ... 94#4513994


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Posted: Wed Apr 10, 2013 7:01 pm 


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