That said, and I'm pretty sure Kraig's data/math supports this, my own math tells me that low Crr makes up for a LOT of "aero sins"...especially if one uses a true "on road" Crr (which takes into account Crr being higher due to surface roughness and the additional hysteretic losses) instead of smooth roller Crr values.

This was seen in the Trek Aerowing data that Damon Rinard originally produced. Despite it's aerodynamics being described as "a mess", the VF Record with it's low Crr still outperformed the narrower and better shaped AeroWing TT 19C up to an apparent wind speed of 20 mph (averaged over all yaw angles - and on an Aelus 50 IIRC).



It's pretty easy to see on that chart above that the GP4000S has the best aerodynamics of the bunch (the curve is the "flattest"), but due to it's worse Crr, it doesn't beat out the aerodynamically challenged VF Record until one reaches apparent wind speeds > 25 mph.

That's what I mean about a low Crr making up for a LOT of "aero sins" ;-)

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http://bikeblather.blogspot.com/

Tom,

I've seen that chart before many times - usually on here of course. But what does apparent wind speed actually mean in the real world? If I am travelling at 25 mph and heading into a 5mph wind (zero yaw, for sake of argument) am I experiencing an apparent wind speed of 30 mph? Or am I being simplistic?

I do find this sort of discussion interesting and have used previous ones along these lines to make certain choices on tyre use. But at the risk of being slung off this forum for suggesting the unthinkable, I have always ended up going back to my Veloflex Records because they 'feel' faster to me and because I always (and I do mean always) do better (measured against other TTers against whom I race regularly) with them on my H3 wheels than when I have run Bonty aerowing 19mm, Conti S/S 20mm, Bonty R4 aero 22mm (though these were best of the rest), PR3 20mm, etc.

What this means is that I have a large stock of very slightly used tyres of various makes in my shed, but that the VR remains my weapon of choice. I use Bonty aerowing 19mm (front) and R4 aero (rear) for unimportant races where durability is more important and switch to the Veloflex Records when I am competing in a target event where I am prepared to trade off the resilience for what I believe is extra speed. Maybe it's the 'feel' of them that raises my morale and causes me to go faster or perhaps this is the effect of the wear on aero tyres being negated very quickly. But this is why I am wondering if I am reading the chart incorrectly (I have best times of 53-13 for 40kms and 20-12 for 16kms, so typically 'see' wind speeds of 27 mph or more when racing)

I've not tried the Zipp Tangente, nor will I because I really don't want any more tyres in my shed.

No, that's not being too simplistic, that's exactly correct :-)

That said, perhaps the chart itself is being too simplistic in that it is trying to show the effects of 3 variables in 2 dimensions, and perhaps this data is best displayed in a 3D chart, or what is sometimes know as a "response surface"...let me explain:

- Rolling resistance force is a function of Crr and ground speed.

- Apparent wind speed and apparent wind angle (i.e. "yaw") are both functions of ground speed, true wind speed, and true wind direction (relative to the rider).

So...ideally, based on the aero drag plots (like Josh posted above) and the Crr values, one would create a plot of "total retarding force" as a function of ground speed, true wind speed, and true wind angle...whoah, I guess that would be a 4D plot!

Now you've got me thinking...Hey Josh, what was the wind speed for that plot above? 30mph? It sure would make things easier if you'd plot those things in terms of CdA ;-)

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http://bikeblather.blogspot.com/

Tom,

thanks for your reply - always valued.

The thought of a 4D model is interesting, but didn't H.G. Wells write something about that?

Seems like my system of going on 'feel' and comparing results with others I race against regularly is as good as I'll ever get. Back to the Veloflex Records for me, then - unless Josh wants to send me some Tangantes for free to add to my great tyre experiment.

Ol Albion - what rims are you using the Veloflex records with? And are you using latex tubes?

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These are on Hed H3s (standard front and Deep rear), so 19mm rims and, yes, I always use latex tubes.

I should add too that I have other race wheels that I do use, but my preference is for the H3s. But I do often use Xentis mark 1 wheels and a Pro (Dura Ace) Disc wheel (with either H3 on the front or a Xentis front). Again, though, contrary to conventional wisdom I do find my results are best when I am on my H3s (rather than using my Disc wheel).

Rolling resistance force is a function of Crr, weight, casing stiffness and inflating pressure

Rolling resistance power is a function of Crr, weight, casing stiffness, inflating pressure and ground speed

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http://cds-0.blogspot.com

Tom,
yes, you are right, that plot would strongly benefit from an additional axis providing yaw relativity, or at least the case for aero tire shaping would be better represented by including a yaw axis as essentially this plot is assuming zero yaw..which we all know to be relatively low probability

Cda is like the metric system, we all know it's better, but it sure seems to confuse the crap out of people when you use in conversation...until we all convert, we are stuck talking in grams..

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Josh,
We have been talking clinchers here. Any thoughts on tubulars tires optimized for 303FC or 404FC tubulars? I imagine the same generalizations hold true ( 22 - 23 width ) but differences with specific brands?

BC

Doh! You are correct. I mis-wrote above...looks like I too fell prey to that common error. Mea culpa.

Thanks for pointing that out though, because now I realize that this data could be easily shown with a 3D response surface showing Ftotal as a function of yaw angle and apparent wind velocity. Excellent!

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http://bikeblather.blogspot.com/

IIRC, the CdA assumed for the Bontrager chart above was an average over some range of yaw...so, in a sense the yaw is included, but as I pointed out above, perhaps in an overly simplistic manner.



I hope you realize the irony of describing CdA as being "like the metric system", and then saying we're "stuck" using a metric unit for force...that's not even a force unit (double irony?) ? :-/

So...was that data taken at 30mph? If so, then I think I should be able to gin up some 3D surface plots of total force as a function of yaw angle and apparent wind velocity :-)

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http://bikeblather.blogspot.com/

I believe it was a blend with an average of around 10 yaw but could be wrong.

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New chain? Really? How many watts can be gained?

TOUR Magazin tests, rolling resistance at 7.5 bars for Conti tires

2011/09
GP Attack / Force : 31.3 watts --> don't know if it's the average of the two tires... I would suppose it is but can't promess anything.
GP 4 season : 40,4 watts.

2010/09
GP 4000 RS : 28.9 watts --> this tire made it to the market only in very limited edition and only in Germany I think.
GP Supersonic : 26.2 watts.

2009/09
GP 4000 RS : 30.1 watts.
GP 4000 S : 33.2 watts.

2008/08
GP 4000 S : 34.1 watts.
Grand Prix : 42.8 watts.

2007/09
GP 4 season : 53.9 watts.
GP 4000 S : 34.4 watts.

The test from Tour has been consistent (at least is seems) over the years (85kg charge, 7.5 bars pressure). So the improvements for a same tire probably came from an improvement (running change) on the tire compounds.
GP 4000S tests the same in 2007 and 2008 and slightly better in 2009. GP 4000 RS tests better in 2010 than in 2009.
Latest result for GP 4000 S in 2009 is 33.2 watts, Attack / Force in 2011 is 31.3 watts. If GP 4000 S kept improving like the others, it's likely in the same range at Attack / Force. What I'd be curious to see is Attack tested alone, maybe the 31.3 watts result come from averaging a 29 watts rear tire (Force) with a 33 watts front tire (Attack). It's very very hard to say, but I've seen in some french magazines the Attack tested slower than the Force so it might make sense.

With all that in mind...
On a non windy / flat / fast day I'd probably go Attack front + GP TT rear. Attack being better at low angles than the others.
On a windy day GP 4000 S front + GP TT rear.
On a bad rainy / windy day probably GP 4000 S both front and rear.

I'd be so curious to see how the Supersonic in 20 and 22 compares (both Aero and RR wise). On clean roads it could probably make for a very good front race day tire !!! Even the 20 on a firecrest rim would probably be "big" enough !

Very good point but we all don't have the mad cornering skills that you have ;)

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Chris Thornham
Co-Founder And Previous Owner Of FLO Cycling

I did a crit on a 19mm tire and didn't die.

Not sure how good my cornering skills are =)

Maybe I will try a 21 in today's crit.

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Kat Hunter reports on the San Dimas Stage Race from inside the GC winning team
Aeroweenie.com -Compendium of Aero Data and Knowledge
Freelance sports & outdoors writer Kathryn Hunter

So, inspired from the Bontager Figure, I wonder: if the Vittoria tyre produces 50 grams of more drag than a michelin pro 3 tyre on a Flo wheel in average across different yaw angles, is it possible based on biketechreviews rolling resistance data to calculate at what what speed the Vittoria tyre can no longer make up for its "aero sins" compared to the michelin pro 3? Would be very interesting to get the opinion from someone a bit better with numbers than myself.

Assuming you aren't a complete non starter fitness-wise, success in crits comes down to 2 factors. Reading a race and bike handling. I don't doubt the best bike handlers in the world could out corner anyone on ST on skinney tires with crappy rubber, but for most of us anything that can give us a bit more cornering confidence and speed is going to overcome the aero advantage of a narrow tire.

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Styrrell

Josh,
Thanks a lot for the great explanation and for the reminder to all of us to ride some tires as close to new as possible on race day !

When you talk about the Tangente being close to GP4000S, are you talking 700x21 or 700x23 ?

Something else I'm curious about is : we've been talking clinchers here, and appart for the Tangente all tubulars are pretty "round". Tubulars tend to sit lower (on recently designed wide carbon rims at least) that clinchers which sit "on top" of it so... does that mean tubular model has less influence than clincher model ? For a same wheel (303 / 404 / 808) are the clincher and tubular version equal in aero or better shape of clincher makes clincher wheel faster or tubular being more hidden inside the rim makes the tubular wheel faster (I know... tough one ;-)) ) ?
At this point if a same wheel is faster in clincher than in tubular then there is really no reason tu use tubulars anymore except for the weight saving which we all know is not a big deal in the equation + bringing a spare tube is lighter than a spare tubular which means total travelling system is at same weight (riding tubulars is about 200gr lighter but bringing a tubular VS a tube is about 200gr heavier...).

Thanks in advance for your answer on both subjects !

Weight isn't the only reason to use a tubular wheelset! How am I suppose to gloat about how much more knowledgable about cycling I am on clinchers?! Hell it doesn't even take 3 days to mount one? How am I suppose to put off training with something that only take 10 minutes to install?

Lol I'm just kidding tubulars corner much better. Yea flame on.

thats good to know that aerobic fitness is not a factor in crit succes as long as you aren't a "non-starter"

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Kat Hunter reports on the San Dimas Stage Race from inside the GC winning team
Aeroweenie.com -Compendium of Aero Data and Knowledge
Freelance sports & outdoors writer Kathryn Hunter

they really don't.
elite national crit champ 2011 - clinchers. winner of the p1 crit last night - clinchers. world tt champ - clinchers

the idea that they corner better usually comes from comparing bad clincher tires to good tubie tires.

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Kat Hunter reports on the San Dimas Stage Race from inside the GC winning team
Aeroweenie.com -Compendium of Aero Data and Knowledge
Freelance sports & outdoors writer Kathryn Hunter

Its not a very big factor. Look at the national crit race for the pros, very seldom has a guy won that also wins other types of races at a high level. LA, Tyler H, Levi, DZ, etc none of them were very succesful at crits and all of them have or had about the biggest aerobic engine in the world. Yet John Tomac won the national championship in virtually his first roadbike race, largely because he was an absolute legend as a bike handler.

There are exceptions. Phinney may have been the best crit rider ever and he did pretty well in other races and Lemond did well in crits but for the most part if you want to win a lot of crits bike handling and reading races is way more important than saving a few watts of CdA or increasing you're FTP, particularly if saving the CdA effect cornering.

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Styrrell

bike handling is certainly important, but taking corners as fast as the local studs, for me anyway, is trivial. its the moving around in the pack without killing anybody that is hard, which isn't much about grip or behavior near the limit of adhesion as it is about some mental skill I don't have!

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Kat Hunter reports on the San Dimas Stage Race from inside the GC winning team
Aeroweenie.com -Compendium of Aero Data and Knowledge
Freelance sports & outdoors writer Kathryn Hunter

keeping up in the corners with the Fisker Karma last night though, was a lot harder:

http://dcmphotography.smugmug.com/...118054&k=89nStqV

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Kat Hunter reports on the San Dimas Stage Race from inside the GC winning team
Aeroweenie.com -Compendium of Aero Data and Knowledge
Freelance sports & outdoors writer Kathryn Hunter