I assume this was Topeak?

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Chicago Cubs - 2016 WORLD SERIES Champions!!!!

"If ever the time should come, when vain and aspiring men shall possess the highest seats in government, our country will stand in need of its experienced patriots to prevent its ruin." - Samuel Adams

Work on your abilities then.

A 2D simulation of that profile is inherently wrong. Think about how the aspect ratio of that shape changes when it is part of a 3d dimension tube at an angle. Same is true of the round shape. A round downtube isn't round as the wind hits it, it is oval.

If you want the ability to verify claims, you have options, here is one:
http://anonymous.coward.free.fr/...cda/indirect-cda.pdf

You can also take a trip and visit EROSports or other TrackAero services: http://ero-sports.com/

Other options would be to trust that a preponderance of independent wind tunnel testing and field testing of entire bikes is more accurate than a flawed 2d CFD simulation of one incorrect slice of an entire bike.

At least use all 3 dimensons!

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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

The research was conducted by Velocite bikes during their uncompleted project to design a bike using genetic algorithms and supercomputers

http://forum.slowtwitch.com/forum/Slowtwitch_Forums_C1/Triathlon_Forum_F1/Velocite_and_Supercomputers_to_develop_most_aero_triathlon_bike_ever!!_P3914706/

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http://cds-0.blogspot.com

Oh god, that thing?
I remember thinking that wasn't going to happen.
It is a neat idea but that scale of that project is really huge.

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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

Definitely helps having someone like Simon Smart from Drag2zero in the UK who has not only designed a lot of the fastest equipment but also has done the position setup for many of the fastest riders.

Bob

Because in real life, it makes a difference. People like to throw highschool physics around and assume a lot of things that downplay weight. That may or may not be your reality. (Hint, you're not a vector and your speed isn't constant)

Sounds like a calibration problem. If properly-calibrated, they will differ by a few %/by a handful of watts due to drivetrain friction. In fact, if you're careful you can detect differences between chainring/cog sizes (e.g., 55 x 11 vs. 60 x 12).

Racing on dual carriageways helps a lot, too.

Hi Chris,

We are pretty familiar with the impacts of mass on acceleration around here. Once again I can point you to tools like analytic cycling, or bestbikesplit, which model acclerations so you can quantify the impact.

Even in crit-like acceleration scenarios aerodynamics tends to vastly outweigh mass, here is one such analysis on wheels by Tom. A:
http://www.slowtwitch.com/...nd_Inertia_2106.html

I can point you to others if you are curious.

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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

Or, the difference between a new chain and an old one...or, a hub with a bad bearing, right? ;-)

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http://bikeblather.blogspot.com/

I picked up on the cassette carrier w/ the bad bearing when field testing revealed an unusually high 'Crr', not by comparing crank- vs. hub-based measurements. But, the magnitude of the effect was large enough that you could have measured it that way as well (assuming you could put the cassette carrier on a PowerTap hub).

If only you were certain your powermeters were both precise and accurate - then you'd know.

I'm man enough to admin when I'm wrong, though I was never really against it. I'm pretty critical of any equipment on my Speed Concept. I still would more than likely go with the EVO because I love the feel and Cannondale's crash replacement is outstanding. If I lose a crit by inch is it the bikes fault? Yeah, I'll have no problem blaming the bike :p

Personally I would like to see more frame testing, with just the raw frame, fork and seatpost and nothing added. Maybe some of those tests are, but for me, bike 'X' is not faster than bike 'Y' when half the equipment is different. I can swap handlebars, wheels, and brakes. Just give me numbers for individual equipment.

Unfortunately the latest frames are designed with equipment and rider interaction in mind, so individual pieces could be misleading.

Like the P5 TT bike tests better with a rider than without, for instance.

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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

Things are not that simple if you want to be methodical enough to study the influence of the frame stiffness on performance.

Tests should be done in a velodrome to remove the influence of the wind. The only way to decouple CdA and Crr is by doing laps at different speeds but the cadence should be constant because the hysteretic energy losses taking place in the tire will be influenced by the number of deflections of the tire per unit time caused by pedalling loads (and to remove the influence of cadence on CdA). If speed is modified while maintaining cadence constant, you need a good model to estimate how drivetrain losses are modified as a function of chainring and sprocket size. A treadmill could be a better option due to all these complications.

Both bikes should have exactly the same wheels, same bearing preload (equal tension on the quick release), same drivetrain, etc.

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http://cds-0.blogspot.com

So it's great for optimising quick release skewer tension.

BTW, Coggan was one of the first to describe testing Crr and CdA using these methods.

I wasn't really talking about wheel weight, although yes that counts. As far as bike weight, how exactly do I type in hundreds of slowing down and speeding up over even a 40k in analytic cycling?

How indeed? Gee, if only there were some way to keep track of all those accelerations and decelerations ....

You don't but you can just simulate one such instance and then multiply that by however many instances to get the total energy or time penalty,

BestBikeSplit will automatically simulate any accelerations due to hills/turns etc which is perfect for TT efforts but doesn't really simulate a crit.

Nobody disputes that less weight is good, the question is whether it is worth it to sacrifice say, 200 grams of mass for .005CdA or not. Or whatever the scenario is.

I can tell you there is almost never a case on flat or rolling terrain where a lighter product wins over a more aero product, even with huge accelerations in the mix (hell, just look at Match Sprinter equipment). Once mountains are in the equation though, of course, lighter can be better.

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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

I am certainly not questioning the value of aero in both frame and fit. What I am pointing out, with no success, is that there are legitimate scientific questions about which design is more aero and whether many bikes marketed as aero are in fact aero at all. Obviously, any who cares about the potential of aero to make them faster wants to ensure they are using the optimum aero design.

The 2d model is just one piece of the much wider, and richer, research data they have come up with. I do not represent the company in any way: I do not even own any of their bikes, so I do not have a stake in their position whatsoever. Moreover, accepted research shows trade-offs inherent to any aero design in terms of how it performs across different wind conditions. Take my bike, the P5-6 as an example. With the wind head on to 5 degrees of yaw, it out performs a Shiv or SpeedConcept. At wider yaw angles, the differences narrow and at some point the aero advantage shifts to the Trek. So which bike is "faster?" It depends on the wind conditions and depends on the rider...the faster one rides, the less impact wind yaw angle will have relative to the bike moving forward through air. So here is a concrete example that shows that even on an objective measure of performance, aero performance of any design can gain in some areas and give in others.

As for my comment about fit, I stand by that. As an age grouper, I have qualified and rode to a good bike split at the Ironman 70.3 World Championships and my bike leg is my strength alongside my swim. With my life schedule and physiology, I have worked very hard to maximize my physical potential within those constraints. Thus, the P5 represents a sound investment to gain a little extra performance....sound reasons for an aero frame as minutes can make a difference between a podium and qualifying slot versus come back and try again. And for elite professionals, Craig Alexander is the poster boy for how much a frame can make a difference at that level. I'm not arguing against any of these advantages of an aero frame! :)

I think the simple point I want to make is a) not all aero is created equal and as consumers we should me more critical of the techno-marketing jargon that passes as "science" and b) people who spend huge money on an aero frames but have not optimized their fit and fitness are spending money on very marginal gains and overlooking potentially massive gains. (Especially on the fit area since a great fit will make you faster and requires no additional training effort, much like buying speed through an aero frame, only the potential gains could be even greater depending on one's original position.) Indeed, other far cheaper ways of buying speed such as more aero wheels, clothing and helmets(aero and suited to the rider's ACTUAL race position) can make a far greater difference than even the most slippery frame. So in the end, I guess what I'm saying is that yes, an aero frame is helpful and makes you faster, but should it be the priority in the hierarchy of things that make you faster? No. It's just another part of a complicated number of variables that matter.

And finally, people who disagree with you are not attacking you...I don't really understand the hostility so evident in many of the replies. It's just the internet...we can all relax and smile knowing we probably share more in common as dedicated triathletes than areas we disagree on!

With a standard forward integration model using the well established mathematical model of the physics of cycling, or something like Robert Chung's virtual elevation modelling.

Since you have a speed reading you know the change in speed, and we can reasonably assume mass doesn't change much from second to second, so for each second you can calculate the change in kinetic energy, which will be 0.5 x mass in kg x (change in speed in metres per second)^2. Power of course is that energy change divided by the duration over which it changes.

Then layer on that the maths for other energy demand factors such as air resistance, rolling resistance, along with changes in gravitational potential energy, and Robert's your father's brother, to coin a paraphrase.

When you do the numbers, you'll quickly realise the power demands for kinetic energy changes during time trial / relatively steady state cycling are very small.

The difference in power demand due to accelerating different masses at the same rate
= 0.5 x (velocity change in metres per second)^2 x (mass difference in kg) / (duration of acceleration in seconds)

e.g. accelerating 1mph in one second (e.g. as if you were going from 20 to 30 mph in 10 seconds), then the power difference of adding 2kg while achieving the same acceleration:
= 0.5 x (1/2.237)^2 x 2 / 1
= 0.2 watts more required to accelerate the 2kg heavier bike.

That fifth of a watt extra is a metabolic bummer. And that's a pretty strong acceleration during a TT, considering most changes in speed are due to variations in gradient and wind, not rider effort.

Let's go a bit more extreme, say 0 to 32mph in 10 seconds. Think track standing start, or a crit with a sharp u-turn.
What's the extra power demand of same acceleration with an extra 2kg on board?
20.5W

So unless your bike leg has lots of sharp U turns and the bike is seriously heavier, I don't think you need be concerned about the impact of accelerating extra mass. The energy demand factors are elsewhere.

I think you need to work on your pacing.

Might be oversimplifying things a bit but we are really talking about approx. 600g here (250-300g real world difference between aero frame and non-aero frame, plus 250g for wheels, and another 50-100g here and there). Carbon is an incredible material and 600g isn't very much at all (less than 1% of rider/bike?).

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