aerodynamic helmets, are they as good as everyone thinks?

[FrankDay]

Recently I went to the wind tunnel to gather some information to help me put my mind around some general aerodynamic principles. One of the questions I wanted to ask was whether an aero helmet was as effective in lowering drag when the head is very low, at the level of the shoulders compared to when the head is sticking up substantially above the shoulders. I took two different readings where I compared road and aero helmet drag numbers for the same position. Here are the positions.

Position 1, the aero helmet lowered the drag 148 grams compared to the road helmet.

Position 2, In this position the difference between the drag with a road helmet and an aero helmet was only 11 grams.

And, position 3, dropping the head even further only saved an additional 11 grams from position 2 (I did not compare the road helmet in this position).

I think this data makes a strong argument that if one has a very good aerodynamic position that an aero helmet offers little improvement and, especially, if the day is hot or the race is long that the rider should consider using a helmet that has better ventilation for improved cooling if one wants to maximize performance.

I would like to know others have data that might counter this observation or other thoughts on this issue.

 

[sciguy]

At the very least, the data your investigation yielded would imply that it's definitely worth testing. In my wife's specific case she consistently rides nearly 1 kph faster while wearing an aero helmet using exactly the same wattage on one of our normal 80km training loops. She does have a rather large head for her size.

Of course we know this because she does every ride with a power meter so every ride is a test session of sorts. That's the great thing about training with a power meter

YMMV,

Hugh

 

[Martin318is]

Interesting but the trick of course is how long you can maintain that very good position or whether you actually move around a bit when actually racing. Its relatively easy to get into a good position for a few minutes but what are you looking like after an hour or more?

Given we have only one data point here, I did a very quick google search on the topic for contrast. Note please that I am NOT arguing in any direction on the topic, just adding info to the conversation.

Craig Alexander Is moving to an aero helmet in Kona for the first time . This seems to be the opposite idea given the heat, etc in that event.

John Cobb Specifically designed the Tomahawk helmet to optimise the aero of Lance's rounded back
Which is a clear pointer that data that works for one rider cannot be simply implied for others.

Dr. San Millán Has some great stuff on aero testing in general but also includes this one gem
"D) While not necessarily a position change, Dr. San Millán says make sure not to forget about an aero helmet, as it will trump every other possible position change, save for what we’ve already mentioned."

As I say, I am not trying to argue one way or the other, although I do believe that the values obtained for one rider on one ocassion are not the basis for anyone with a 'perfect' aero position to throw away the expensive helmet and wear a standard road helmet instead.

One thing that IS true is that its worth looking at real testing for real riders, rather than relying upon grand claims in marketing such as this: Apparently Greenedge won because of their helmets! Wow

 

[CoachFergie]

Have never found the aero helmet to be worse than a normal helmet. Our local importer is always doing deals so it's very cost effective. Riders do need to be coached to not look down or around while riding otherwise the drag will shoot up.

 

[Kiara is a rational girl]

Position 3 tests a change in position. Doesn't exactly seem relevant in a thread about helmets, lol.

I don't see how you got a 187 gram saving using the aero helmet in position 1, and only an 11 gram saving in position 2 when the head/helmet is only slightly lower relative to the body. But whatever. I'd still rather wear an aero helmet than run absurdly short cranks.

In my wife's specific case she consistently rides nearly 1 kph faster while wearing an aero helmet using exactly the same wattage on one of our normal 80km training loops.

hahaha, what a dork.

Have never found the aero helmet to be worse than a normal helmet. Our local importer is always doing deals so it's very cost effective. Riders do need to be coached to not look down or around while riding otherwise the drag will shoot up.

Really? I read that riding with the head down is faster, although only because the vents are no longer exposed to the wind.

 

[FrankDay]

Position 3 tests a change in position. Doesn't exactly seem relevant in a thread about helmets, lol.

The reason I included position 3 is the very small improvement seen from that seemingly substantial lowering suggests to me that there could have been conceivably zero difference between the road and aero helmet had I measured it.

I don't see how you got a 187 gram saving using the aero helmet in position 1, and only an 11 gram saving in position 2 when the head/helmet is only slightly lower relative to the body.

It was a 148 gm difference not 187, which is still substantial. Works out to about 20 watts savings at 30 mph (the speed in the tunnel) whereas the lower position only saved about 1.5 watts.

 

[acoggan]

Fact: not all aero helmets are created equal, and not all aero helmets work the same in different positions/on different individuals. To even pose the question "aerodynamic helmets, are they as good as everyone thinks" based on n=1 tests of unknown precision is therefore quite naive.

(A bit of related background reading, in case anyone is interested: http://dspace.mit.edu/bitstream/handle/1721.1/40486/191803811.pdf)

 

[FrankDay]

Fact: not all aero helmets are created equal, and not all aero helmets work the same in different positions/on different individuals. To even pose the question "aerodynamic helmets, are they as good as everyone thinks" based on n=1 tests of unknown precision is therefore quite naive.

(A bit of related background reading, in case anyone is interested: http://dspace.mit.edu/bitstream/handle/1721.1/40486/191803811.pdf)

Asking the question as to whether the effectiveness of a helmet varies in relation to the position of the head related to the shoulders based on an n=1 is naive? I actually asked the question to myself based on an n=0. That is really naive I guess. LOL. Except the data I got suggests there is something to it. Do you have any data to counter my finding?

Anyhow, I noted that your "related background reading" paper did not address the question being asked here and only supports what I found, the benefits are substantial when the head is sticking up above the shoulders. If only you could join some of these threads and actually add something useful rather than trying to show everyone how smart you are.

 

[CoachFergie]

Really? I read that riding with the head down is faster, although only because the vents are no longer exposed to the wind.

Depends on the model, the position and the rider. Some models have no vents or are taped up. This is why n=1's are naive.

 

[twothirds]

My sister got T-boned the first time she got behind the wheel of a car. Does this mean that she should believe it's reasonable to think that because she is 1 for 1 in that situation that this will be true every time she get's behind a wheel and drive? No. Statistics are nice to look at in hindsight, but they immediately get thrown out the window for each individual situation. If you know that these things are highly individual, and have stated such, then stop questioning common sense.

 

[acoggan]

Asking the question as to whether the effectiveness of a helmet varies in relation to the position of the head related to the shoulders based on an n=1 is naive?

1. That isn't the question you asked in starting this thread.

2. The question you ask above was answered a long time ago. If you'd bothered to do a bit of research and/or spoke with experienced people before going to the wind tunnel, you'd have known that, and not wasted your time attempting to reinvent the wheel.

P.S. The best helmet for your client in his most head-up position would almost certainly be a Uvex, whereas the original LG Rocket would likely work very well when his head is its lowest position. The single aero helmet that was tested is sort of neither here nor there...

 

[FrankDay]

1. That isn't the question you asked in starting this thread.

Huh? From the original post:

One of the questions I wanted to ask was whether an aero helmet was as effective in lowering drag when the head is very low, at the level of the shoulders compared to when the head is sticking up substantially above the shoulders.…I would like to know others have data that might counter this observation or other thoughts on this issue.

2. The question you ask above was answered a long time ago. If you'd bothered to do a bit of research and/or spoke with experienced people before going to the wind tunnel, you'd have known that, and not wasted your time attempting to reinvent the wheel.

Why don't you direct us to that work if it has already been done?

P.S. The best helmet for your client in his most head-up position would almost certainly be a Uvex, whereas the original LG Rocket would likely work very well when his head is its lowest position. The single aero helmet that was tested is sort of neither here nor there...

We weren't testing the best helmet. Thanks for that information though, I guess.

 

[Martin318is]

We weren't testing the best helmet. Thanks for that information though, I guess.

That wasn't his point though really. His point was that you are asking this question based upon one rider with one aero helmet vs one road helmet.

If you had done the testing to find the best helmet for this rider rather than just comparing the two you had, the likely differences in drag between that helmet and the road one in each position would mean that you wouldn't be asking the question in this thread.

 

[FrankDay]

That wasn't his point though really. His point was that you are asking this question based upon one rider with one aero helmet vs one road helmet.

If you had done the testing to find the best helmet for this rider rather than just comparing the two you had, the likely differences in drag between that helmet and the road one in each position would mean that you wouldn't be asking the question in this thread.

The question I had before I went to the tunnel was: Does the advantage of an aero helmet diminish as the rider gets lower and lower. I wanted to ask that question because one of the seeming advantages of shorter cranks that I saw was they facilitated riders being able to achieve very low positions. I thought it might be interesting to look at that question also since I expected to have my rider in some very low positions. Because I was limited for time I only tested two positions, one high and one pretty low, but not the lowest achieved. And, I measured the savings offered by this particular helmet changed from about 20 watts to 1.5 watts, something that really caught my eye since this was not the lowest position I was able to achieve.

While my data is not a definitive answer to any question it does seem to me that this data should cause anyone who has a particularly aero position to at least ask the question as to whether they might also be seeing similar very small benefit and whether the loss of cooling is worth the trade-off. Yes, it is only one rider, but that one rider was in a wind-tunnel under tightly controlled conditions. And, isn't that the case with every rider who might ask the question, would this apply to me?

Dr. Coggan doesn't seem to have a clue as to what I was trying to accomplish here but felt like he should chime in with some information that he thought important, even though he hasn't presented a single "fact" that is of any relevance to the question that I was asking in this test.

 

[CoachFergie]

Dr. Coggan doesn't seem to have a clue as to what I was trying to accomplish here but felt like he should chime in with some information that he thought important, even though he hasn't presented a single "fact" that is of any relevance to the question that I was asking in this test.

These questions were well answered by the research Andy provided a link for. It's amusing you find the obvious result that an aero helmet makes less difference in a more aero position noteworthy. I have yet to see any data showing an aero helmet to be worse than a regular helmet.

With regards to cooling it appears to have been answered by Mark Cavendish who won Worlds last year using a helmet cover and the Sky team this year who raced the classics using helmets with no vents. One would expect as the weather warms up the covers will come off the the helmets with vents will reappear.

I haven't compared these helmets with regular or aero helmets yet. Will be something to do on my next visit to the tunnel.

 

[STODRR]

Really? I read that riding with the head down is faster, although only because the vents are no longer exposed to the wind.

I believe he might have been saying looking down which makes the tail go up into the wind stream, not moving your whole head down.

 

[Kiara is a rational girl]

I believe he might have been saying looking down which makes the tail go up into the wind stream, not moving your whole head down.

That's what I thought he meant. On my part, 'head down' is ambiguous and I could have phrased that better.

 

[acoggan]

As a public service announcement, below are some of the studies Frank could have consulted before performing his experiment. If he had done so, he would have realized that he was really just wasting his (client's?) time comparing a road helmet to just one aero helmet, and instead could have used it to find the aero helmet that worked best for that individual.


1. Kyle CR (1989). The aerodynamics of helmets and handlebars. Cycling Sci 1: 122–125.

2. Chin KY, Lim LK (2001). The design of an aerodynamically sound biker’s helmet. Department of Mechanical Engineering, University of Adelaide, Adelaide.

3. Blair K, Sidelko S (2008). Aerodynamic performance of cycling time trial helmets. In: Estivalet M, Brisson P, eds. The Engineering of Sport 7, New York: Springer, pp. 371-377.

4. Chabroux V, Barelle C, Favier D (2008). Aerodynamics of time trial cycling helmets. In: Estivalet M, Brisson P, eds. The Engineering of Sport 7, New York: Springer, pp. 401-410.

5. Brownlie L, Ostafichukb P, Tews E, Muller H, Brigg E, Franks K (2010). The wind-averaged aerodynamic drag of competitive time trial cycling helmets. Procedia Eng 2: 2419–2424.

6. Chabroux V, Nsi Mba M, Sainton P, Favier D (2010). Wake characteristics of time trial helmets using PIV-3C technique. 15th Int Symp on Applications of Laser Techniques to Fluid Mechanics. Lisbon, Portugal, 05-08 July, 2010

 

[acoggan]

As a public service announcement, below are some of the studies Frank could have consulted before performing his experiment. If he had done so, he would have realized that he was really just wasting his (client's?) time comparing a road helmet to just one aero helmet, and instead could have used it to find the aero helmet that worked best for that individual.


1. Kyle CR (1989). The aerodynamics of helmets and handlebars. Cycling Sci 1: 122–125.

2. Chin KY, Lim LK (2001). The design of an aerodynamically sound biker’s helmet. Department of Mechanical Engineering, University of Adelaide, Adelaide.

3. Blair K, Sidelko S (2008). Aerodynamic performance of cycling time trial helmets. In: Estivalet M, Brisson P, eds. The Engineering of Sport 7, New York: Springer, pp. 371-377.

4. Chabroux V, Barelle C, Favier D (2008). Aerodynamics of time trial cycling helmets. In: Estivalet M, Brisson P, eds. The Engineering of Sport 7, New York: Springer, pp. 401-410.

5. Brownlie L, Ostafichukb P, Tews E, Muller H, Brigg E, Franks K (2010). The wind-averaged aerodynamic drag of competitive time trial cycling helmets. Procedia Eng 2: 2419–2424.

6. Chabroux V, Nsi Mba M, Sainton P, Favier D (2010). Wake characteristics of time trial helmets using PIV-3C technique. 15th Int Symp on Applications of Laser Techniques to Fluid Mechanics. Lisbon, Portugal, 05-08 July, 2010

Also:

Alam, F., Subic, A. & Akbarzadeh, A. (2008). Aerodynamics of bicycle helmets, in M. Estivalet
& P. Brisson (eds), The Engineering of Sport 7, vol. 1, Springer, Paris, pp. 337–344.

 

[CoachFergie]

And a ton of other studies on helmet aerodynamics and thermal efficiency. While it is commendable that people want to test theories part of the scientific process is to gather information from research already performed.

 

[Alex Simmons/RST]

Just to add to the findings that it really does depend on the individual, when testing helmet options for myself and others, I have not found a consistent answer to the issue of whether the difference is bigger based on head position of the rider, certainly not on which helmet is best for any particular rider.

Indeed of all the riders I've tested, I've probably got as much head sticking up as any of then, yet I gain the least benefit from an aero helmet - at least when assessing the helmets I had available to test (Met mass start, Specialized, Giro, Uvex).

One of my clients (the master hour record guy) gained the most from appropriate helmet choice yet his head is lower relative position than mine. And in that position there were substantial differences between aero helmets, let alone a standard mass start helmet.

 

[FrankDay]

Just to add to the findings that it really does depend on the individual, when testing helmet options for myself and others, I have not found a consistent answer to the issue of whether the difference is bigger based on head position of the rider, certainly not on which helmet is best for any particular rider.

Indeed of all the riders I've tested, I've probably got as much head sticking up as any of then, yet I gain the least benefit from an aero helmet - at least when assessing the helmets I had available to test (Met mass start, Specialized, Giro, Uvex).

One of my clients (the master hour record guy) gained the most from appropriate helmet choice yet his head is lower relative position than mine. And in that position there were substantial differences between aero helmets, let alone a standard mass start helmet.

Thanks for imparting your experience. It seems to me that there must be some principles that we might be able to extract if we had enough data. Do you think you have enough experience that you can predict, before the rider is in the wind tunnel, what the results might be for any particular rider?

 

[Alex Simmons/RST]

Do you think you have enough experience that you can predict, before the rider is in the wind tunnel, what the results might be for any particular rider?

No.

My reasonable SWAGs have been proven wrong by actually collecting the data.