November 24, 2014 Login  


these newfangled aero helmets...
Last Post 04/22/2014 04:16 PM by Keith Jackson. 95 Replies.
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Keith Richards

Posts:755

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03/27/2014 09:30 PM
Look, if the average racer actually believes that their helmet is going to make a two bike length difference in their sprint...I just saw an ad that said it could add 2".

The irony of you pulling that out is that chart is my exhibit "A" for the ridiculousness of this aero thing for the average recreational racer.

So yeah, you finished 13th in the 1/2/3 race by a wheel. Thanks to your helmet.

----- It is his word versus ours. We like our word. We like where we stand and we like our credibility."--Lance Armstrong.
Cosmic Kid

Posts:1172

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03/27/2014 10:31 PM
Well, I never said that an aero road lid will make a winner out of someone who is middle of the pack. Clearly it won't....but it is gonna make you faster.

You asked for evidence that it makes a real world difference....I gave you evidence (albeit Specialized's) that show a significant difference in a sprint. Unfortunately it is impossible to test these things in "real world" situations because you can never duplicate such a sprint exactly. So you have to rely on the data that is repeatable and extrapolate.

There is a company called ERO sports that does aero testing on the velodrome, so it is a bit more "real world" than a wind tunnel (although you lose the ability to test at yaw angles)....all their tests have shown the Evade to be significantly faster than a road lid and faster than many TT lids. ERO is independent and develops their own testing criteria....but they don't publish the actual data since it is usually commissioned by other companies or individuals.

If I was racing right now, I would absolutely rock an Evade....assuming I could find one, of course. Damn things are impossible to find right now.
Just say "NO!" to WCP!!!!
Keith Richards

Posts:755

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03/28/2014 11:05 AM
Posted By Cosmic Kid on 03/27/2014 10:31 PM
So you have to rely on the data that is repeatable and extrapolate.



As a person who deals with scientific studies I have a problem with data that is generated with so many variables left unaddressed, unaccounted for or not reported. If someone want to rely on that data to inform their helmet purchase for mass start racing, that is their bag. I will take a pass. Especially at that price point.
----- It is his word versus ours. We like our word. We like where we stand and we like our credibility."--Lance Armstrong.
Cosmic Kid

Posts:1172

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03/28/2014 05:12 PM
I think you are misrepresenting the data generated from wind tunnel tests a bit. It is controllable and repeatable, which is the goal with scientific testing. It also presents as complete a overall picture as possible. Extrapolating data is also an accepted practice.
Just say "NO!" to WCP!!!!
Ride On

Posts:452

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03/28/2014 06:51 PM
Most wind tunnel testing I've seen ignores the fact that cyclist rock side to side when pedaling. Wind tunnel data is great for cars, planes, boats that move forward without a lot of side to side motion.

When you get flow over a stationary object it's not the same as flow over an object to is pitching side to side perpendicular to the direction of the flow.

They ignore it because adding that degree of freedom makes the problem harder to solve.
Orange Crush

Posts:1233

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03/28/2014 07:05 PM
I was just reading an article where they for first time used computational fluid dynamics (CFD) to look at problem of how much drafting saves in energy when riding in a group. This was first time someone was able to look at that question with state of the art CFD. Yet, some of the assumptions they had to make were pretty laughable.

The one interesting outcome was that riding in a peleton not only is better for guys drafting but also for the front guy just because of way air moves around group as a whole. Oh, and also, the best position in a reasonably sized group is second to last. But obviously that is only from an aero perspective, it ignores the elastic band effect.

As Keith said, so many variables in a race. There is a lot of random motion going on in a peleton which will tend to negate/reduce a lot of benefits one can get from equipment, none of which is incorporated in either wind tunnel testing of CFD.

And for us commoners, the benefits always get overstated cause the numbers provided are always for top end speed where gains are greatest (that 2 m on a 200 m sprint is @ 1000W).
Cosmic Kid

Posts:1172

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03/28/2014 08:24 PM
Except that a lot of wind tunnel testing is done with riders actually pedaling a bike at power....IOW, they are riding as they would on the road.

No, it is not all WT testing, but a lot....

The data is out there...aerodynamics play a larger role in performance than we previously thought / believed. And helmets are one of the best, fastest and cheapest way to get some additional watts.
Just say "NO!" to WCP!!!!
Orange Crush

Posts:1233

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03/28/2014 08:35 PM
Yes, pedaling a bike at power and all that but sitting still otherwise.

This is a nice article
http://www.bicycling.com/bikes-gear/bikes-and-gear-features/wind-tunnel-obsolete

"Talk to enough people in the bike industry and, perhaps after a beer or two, they’ll admit that wind tunnels are finicky and produce impossible-to-replicate results. They use simplistic environmental conditions that don’t reflect the complexity of real-world conditions, from how a rider may shift position under a hard effort to the way that crosswinds can swirl around an object."

Back to the sprint, its almost never in a straight line is it. Lot of random motions in that sprint.

Maybe a wind tunnel replicates a tri effort
Cosmic Kid

Posts:1172

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03/28/2014 10:10 PM
Seriously? We are citing Bicycling magazine? Was this article in the same issue as the "12 Weeks to Your Best Century" plan? Oh wait....that is EVERY issue.

Seriously though, I never said WT testing was perfect....but it is the best tool available. And the idea that it can't replicate crosswinds is flat-out wrong.

I don't buy any of the specific claims that companies make as it pertains to time saved, etc. Way too specific and can't replicate the actual changing wind conditions on a course, etc. But it absolutely can tell you that aero road lids are faster than standard road lids. We can quibble all day about how much faster, but the data that it is, indeed, faster is irrefutable.

So my question is very simple - why would you choose equipment that you KNOW is slower when evaluating equipment options? Conversely, why wouldn't you choose equipment that can give you an advantage over your competition?

My prediction - within 3 years (5 at the outside) every single person on this board who races will be in an aero road lid.
Just say "NO!" to WCP!!!!
Orange Crush

Posts:1233

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03/29/2014 12:43 AM
It's only the likes of Cervelo and Mavic that are realizing the limitations of wind tunnels and are looking for these alternatives CK. You would have got that if you chose to read the article :-P

And you would also have gotten the point that it is not that wind tunnels can't do crosswinds, the point is wind tunnels don't do rapidly varying conditions that one sees in the real world. That's exactly their downfall. Everything in a wind tunnel is steady. That's how the experiments are set up. Idealized conditions.

I'm not doubting that these new lids are faster but when someone starts posting examples of 2 m gains on a 200 m sprint under a set of highly idealized conditions never to be replicated in reality then that's time for some serious hoho.

If we cannot buy the claimed advantage of these aero lids, then the key question becomes, what is the actual advantage of those lids? Marketing hype or is there some real marginal advantage and that is the magnitude of that advantage?

Your prediction is probably right simply because the market is getting flooded.
Ride On

Posts:452

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03/29/2014 06:12 AM
Agree with OC. The "data" you are seeing is marketing data and people buy products based on marketing all the time.
Cosmic Kid

Posts:1172

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03/29/2014 10:55 AM
OC, I specifically noted the limitations of WT in terms of translating that to real-world conditions. This is exactly why I don't buy into claims that say "xxx seconds/ minutes saved." People always want to know which *insert product here* is "fastest". The answer is "no one knows." But you can determine which products are "faster."

IOW, the data can be taken directionally to make informed choices. If I am in the market for a new helmet, and I am a bike racer, why wouldn't I seriously consider a helmet that makes me "faster"? In a sport where the differences can be the width of a tire, seems like it would be a smart choice.

Here is an example I have used before - Cancellara winning stage 3 of the 2007 TdF. He is on the Cervelo S3 and wins the stage by the slimmest of margins. Wild he have won had have been on an R3 (round tubes)? Dunno....but I'll betcha he was glad he was on the S3.

http://m.youtube.com/watch?v=BJNLMYpr2TM

The gains made by wearing an aero lid are real, measurable and significant. This has been proven time & time again. In the wind tunnel (and on the velodrome), some aero road lids have been shown to produce results just below those of full TT lids. Given that, can you explain what laws of physics would make these helmets not have speed advantages over standard road helmets in the "real world"?



Just say "NO!" to WCP!!!!
jacques_anquetil

Posts:230

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03/29/2014 11:19 AM
thanks for filling the sails of this discussion, fellas! (on second thought, that's probably a poor metaphor choice.)
Orange Crush

Posts:1233

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03/29/2014 11:25 AM
"I specifically noted the limitations of WT in terms of translating that to real-world conditions."

"The gains made by wearing an aero lid are real, measurable and significant."

Sighhh...science and marketing is like science and politics.

Where do I claim there newfangled lids are not faster? What I question is the term "significant". I am going to tell you that statement would not hold up if one wanted to publish current data in a scientific setting.
Funk

Posts:22

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03/29/2014 11:55 AM
I saw a guy wearing a time trial helmet on RAGBRAI a few years back. For those of you unfamiliar, RAGBRAI is a leisure ride where you shuffle along 10 miles at a time and then eat pie and drink beer for an hour. I think this is the crux of why some of us get cranky re: aero this and lightweight that. 99% of cyclists will never get to the point where an aero lid will make much of a difference. I think CK is right, technically. They are probably a little bit faster. Makes sense. If I'm Cancellara or Tony Martin or whomever, yes, absolutely. If I'm a cat 4 farting around on the weekend, I'm probably flushing money where I shouldn't be. My .02 cents.
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