Advocacy & Safety - Do helmets really keep you (your head) COOLER?

Is this a marketing strategy or does it work?

I can see it adding shade, but not much else.

Is this a marketing strategy or does it work?

I can see it adding shade, but not much else.
Helmets and their alleged benefits are all about marketing strategy and the customers (including non cycling public) who buy it.

Is this a marketing strategy or does it work?

I can see it adding shade, but not much else.

I don't know. But the helmet foam is great insulation. Shade does make a difference.

I think in the nice weather it's not letting the heat out of the top of your head if you are working hard.

Do helmets really keep you (your head) COOLER?
On a ride without a helmet on a hot, sunny day I'd be wearing a light-colored cycling cap and wetting it down periodically. That provides pretty effective cooling and I can't see a helmet coming close.

But the helmet might be cooler than not having any head covering on a sunny day.

They wear pith helmets and turbans in the desert for that purpose, to keep the sun off the old noggin. Those pith helmet and turban manufacturers must have pretty good marketing to sell keffiyehs to Bedouins...

Taylor Phinney is definitely in on the scam...

http://velonews.competitor.com/2011/02/news/taylor-phinney-recovering-from-concussion-after-crash-in-italy_161767

Ya know, whenever I can keep the sun from shining on my head directly, it helps. A helmet with good ventilation has enough airflow to let my head stay cooler, too. My favored hot-weather hat -- not a bike helmet, but a straw hat with a wide brim -- provides both shade and ventilation.

I certainly feel more comfortable on hot days with my S-Works than with my Bell Metropolis. Almost as good as standing around with that straw hat, too.

I too use to have a Bell Metro, but the new Lazer is far cooler. Bare head riding vs helmeted head for coolness? I don't know, I think have a brain protected is more important then whether or not the heat is hotter with the helmet off or on...but the helmet does look a bit odd on my ashe.

Is this a marketing strategy or does it work?

I can see it adding shade, but not much else.

I certainly think it keeps my head cooler.

Helmets and their alleged benefits are all about marketing strategy and the customers (including non cycling public) who buy it.

Hit your head once in accident and see how you feel about that!

No

styrofoam is an insulator, it may keep the heat of the sun out but it also keeps the heat your body is trying to dissipate in.

the top of the head is a major hot spot on the human body, where excess body heat is expelled, it needs ventilation, not encasement in insulation

No

styrofoam is an insulator, it may keep the heat of the sun out but it also keeps the heat your body is trying to dissipate in.

the top of the head is a major hot spot on the human body, where excess body heat is expelled, it needs ventilation, not encasement in insulation

I thought that was debunked a few years ago in the British Medical Journal.

Since we're all just offering our untested opinions, I'll jump in. Yes the magic styrofoam is an insulator, but most helmets are designed to have only a couple points of contact with substantial airflow channeled between the head and the foam. Thus whether it is cooler or not depends on the amount of sunlight energy blocked relative to the amount of airflow blocked. I've had pieces of magic stryofoam that seemed hotter than going helmetless and I've had ones that seemed cooler. I would guess one's hair length/style/existence would be a more significant factor in head coolness. I really don't see how this is a make or break feature of the decision to don a helmet or not. I suppose we'll soon see ads touting the U.V. blocking properties of helmets too.

I've ridden in hot weather both with and without (without does involve the use of a ball cap), and without is cooler. My hair is a little thin on top, so a sunburned pate is distinctly possible. Therefore, the cap.

Helmets DO, however, provide some ventilation, I've experienced it. Just not as much as WITHOUT.

Chris516, take the helmet safety argument elsewhere, there's plenty of space already devoted to it.

Depends on your choice of helmets and your riding speed.

Higher end helmets have more vents that are better designed to try to achieve a more laminar flow.

At very low speeds, neither a low or high end helmet gets much air flow. But then a bare head, at low speed does not get much air flow.

My experience is that a better helmet at >15 mph give more cooling and is about the same as a wetted skull cap.

Prior to climbs (slow speed), I just squirt a little water through the helmet vents to keep cool during the climb (make sure to use the bottle with water and not the one with sports drink).

It definitely feels much hotter with the helmet on. But then I never could stand to wear any headgear in the sun -- it just seems to make things worse for me.

Personal experience -- my first helmet looked like the one in the first pic. Didn't vent very well, so it indeed was a decent insulator.

The second pic, a Bell Metropolis, vents so-so. I still have it because of its neat snap-on rain cover, which then turns it into a non-ventilated helmet. I wonder if I'll ever find a winter kit for it, making it super-insulating. :p

The third, a Specialized S-Works, vents better than either a Giro Xen (which was my first new helmet in nearly ten years; still have it but hardly use it) or a Giro Pneumo (gave it to a neighbor who needed a new helmet). MSRP is awfully high, but I got a great deal on mine, or else I probably wouldn't have bought it. The "mega mouthport" hole in the front is probably half the reason it vents so well, and most other Specialized helmets have it, too.

http://www.prorider.com/org/images/10VBlue80.jpg
http://www.thebicyclebum.com/parts/bellmetrohelmet468x338.jpg
http://www.ae7.com/components/com_virtuemart/shop_image/product/b59cce38a0eeebd28ed16a7809abc14b.jpg

jesus. Next thing you know, helmet makers will claim that bicycle helmets can cook your eggs over easy, too.

This claim is really the response to the increasing failure of the helmet = safety claim. Gotta find some way to sell them plastic hats!

At least I can say that I've personally tried a variety of helmets under all weather conditions.

Don't know about cooler, but my new (as of last summer) Specialized helmet did save me a bee sting--the front-to-back ventilation is so direct that a bee blew clean through on a descent on a grade down into Colville, WA.

but my mom says i'm cool

At least I can say that I've personally tried a variety of helmets under all weather conditions.

so have I... well, I've tried 2 helmets anyways. A Bell V-1 Pro followed by a Bell Image.

I had read all the stories that said the venting made your head cooler with a lid than without and thought they made sense, but when I finally took my helmet off after wearing it for 21 or so years, I was pleasantly surprised at how much cooler it was without.

Now that I'm wearing the good 'ol Canadian touque, it's warmer in the winter too.

When it is hot and sunny out it keeps it cooler than none, like a hat would.
When it is cold to warm out or not sunny it makes ones head feel warmer than none.

Don't know about cooler, but my new (as of last summer) Specialized helmet did save me a bee sting--the front-to-back ventilation is so direct that a bee blew clean through on a descent on a grade down into Colville, WA.

I caught a bumble bee in my specialized helmet last fall. Felt the thunk on my head, thought I still felt something a block down the way, pulled over and took my helmet off: There he was all nuzzled up against the helmet. I'm scared to death of bees, but I'll be damned if he wasn't cute. Turned the helmet upside down and gave him a gentle tap, and he flew off. I kind of wonder how much of it was shock and how much was him liking the warmth of my head on a cold day.

Moral of the story: Bumble bees aren't very threatening when it's 40F and you've taken them off their planned route. And even the most vicious things can be cute when they're cuddled up.

Since I ride a recumbent I wear a helmet with a sunvisor That plus the fact I always buy a white helmet with good venting seems to make me cooler.

I have never understood anyone buying a dark colored or worse yet a black helmet. They will just heat up in the sun. A lot of people want to look pretty or be "stylin" rather than use common sense.

Another thing to consider...

Helmets have a greater surface area than your head, so if properly designed the vents could be directing more air over your head than would otherwise hit your bare head. Whether or not that increased airflow(if it exists) + sun shading will overcome the insulating properties of the foam I don't know.

Depends on your choice of helmets and your riding speed.

Higher end helmets have more vents that are better designed to try to achieve a more laminar flow.

At very low speeds, neither a low or high end helmet gets much air flow. But then a bare head, at low speed does not get much air flow.

My experience is that a better helmet at >15 mph give more cooling and is about the same as a wetted skull cap.

Prior to climbs (slow speed), I just squirt a little water through the helmet vents to keep cool during the climb (make sure to use the bottle with water and not the one with sports drink).

Laminar flow is the opposite of what you want for cooling.

Also, I don't see any practical way that a helmet can convectively cool more than a bare head. All of the air flow in a helmet is coming from the free air stream around you. Air vent designs are basically a manifold that diverts that free air stream under the helmet and over your head. At best, this could achieve the same thing as a bare head, you get the free stream air velocity whooshing over your locks. At worst it loses most of the velocity to aerodynamic effects and friction and has a much smaller cooling surface area. The argument might have merit when you include shading with the helmet exterior acting as a big radiator. It couldn't radiate your own heat though because of the stryofoam.

Another thing to consider...

Helmets have a greater surface area than your head, so if properly designed the vents could be directing more air over your head than would otherwise hit your bare head. Whether or not that increased airflow(if it exists) + sun shading will overcome the insulating properties of the foam I don't know.

I won't say that any helmet could increase airflow compared to no helmet, but the "properly designed" part makes a big difference. I mentioned the Pneumo and S-Works helmets earlier and how the S-Works vented better. Looking at them now, I notice that the S-Works is basically a series of longitudinal ribs with air channels between them, while the Pneumo's channels are more convoluted. Wind coming through the S-Works basically has a straight shot from the front to the back.

I'd venture to say that since the airflow is so good, and how it's still deep enough to provide shade at most angles, it's at least as good as wearing a ballcap.

http://briko280.blogspot.com/2010/11/giro-pneumo.html
http://4.bp.blogspot.com/_A7QYCOUtiuU/TM-Fv2svmTI/AAAAAAAAKNA/YTWUfBbkDdE/s1600/Giro-Pneumo+White14.jpg
http://sprinterdellacasa.blogspot.com/2008/03/preview-2008-specialized-s-works-helmet.html
http://mountain.bike198.com/wp-content/uploads/2010/05/specialized-s-works-6.jpg

Laminar flow is the opposite of what you want for cooling. That is wrong because turbulent flow is less efficient at moving the heat away than laminar flow. Which result in a smaller temperature differential for your heat exchange and therefore less heat exchange.

In certain closed systems, turbulent flow can result in a faster equalization of temperature. But the airflow across your head is NOT a closed system.

That is wrong because turbulent flow is less efficient at moving the heat away than laminar flow. Which result in a smaller temperature differential for your heat exchange and therefore less heat exchange.

In certain closed systems, turbulent flow can result in a faster equalization of temperature. But the airflow across your head is NOT a closed system.

Did you just make this up? I study fluid dynamics, and I have never seen an equation or a model or an experiment where laminar flow transfers more heat than turbulent flow. Can you suggest a mechanism?

By common sense, turbulent flows have more mixing going on. They have more diffusion of momentum and mass, and therefore heat as well. If a temperature gradient exists such as between your head and a free stream of air, the turbulent flow will have a greater heat transfer coefficient than the laminar flow, cooling your head more.

http://en.wikipedia.org/wiki/Turbulence#Heat_and_momentum_transfer

When flow is turbulent, particles exhibit additional transverse motion which enhances the rate of energy and momentum exchange between them thus increasing the heat transfer and the friction coefficient.

Gee, I guess I had better go tell all those engineers designing nuclear reactors for the navy and civilian power plants that they screwed up.

No, I did not just make that up. In a closed system, as I said, the energy transfer within the fluid is higher for a finite time until the system reaches equilibrium. But your head is not not in a closed system. It has a constant flow of new fluid across it which maintains the fluid temperature that is in contact with your head and a higher temperature differential across the boundary. If you introduce turbulent flow, you reduce the overall flow rate over the head and thereby reduce the temperature differential across the boundary.

For this situation, the only function that matters is the energy transfer across the boundary and not the energy transfer from mixing within the fluid.

but really, it's just cooler on your head when you don't wear a helmet, than when you do. Just try it.

We all know closet hates helmets. He will be for any argument against them. So closet---------------how do you argue against helmets for bald cycist that dont want to sunburn their heads.

We all know closet hates helmets. He will be for any argument against them. So closet---------------how do you argue against helmets for bald cycist that dont want to sunburn their heads.

Baseball cap works for me, keeps the sun and rain off my face and glasses. No off bike storage issues either. Doesn't break apart when dropped, no shelf life, no UV/ozone deterioration issues. Easy to keep clean and smell free too! No helmet hair or wacky tan patterns.

Helmet needed to protect against sun burn and excess heat? Who wudda thunk it, eh?

Its probably a toss up in the blazing sun on a hot day, but I know for sure that this time of year, my head is hotter in a helmet. The first thing I do when I get to work is rip it off so I can start cooling down. The more expensive helmets are better, I'm sure, but the main problem is the natural evaporative cooling you get from sweat is lessened with a helmet on.

We all know closet hates helmets. He will be for any argument against them. So closet---------------how do you argue against helmets for bald cycist that dont want to sunburn their heads.

Have you tried coating your scalp with oil and wrapping it in tin foil? You might want to add some cream cheese when you are almost done...

Failing that, you could try a hat.

Gee, I guess I had better go tell all those engineers designing nuclear reactors for the navy and civilian power plants that they screwed up.

No, I did not just make that up. In a closed system, as I said, the energy transfer within the fluid is higher for a finite time until the system reaches equilibrium. But your head is not not in a closed system. It has a constant flow of new fluid across it which maintains the fluid temperature that is in contact with your head and a higher temperature differential across the boundary. If you introduce turbulent flow, you reduce the overall flow rate over the head and thereby reduce the temperature differential across the boundary.

For this situation, the only function that matters is the energy transfer across the boundary and not the energy transfer from mixing within the fluid.

No one said that your head is a closed system: you are being silly.

As for the flow of air past your head when riding a bicycle, prepare yourself for a shock: IT WILL BE EXACTLY THE SPEED YOU ARE MOVING AT! Neglecting the wind that is. This will apply whether it is turbulent or laminar. What will change is that amount of drag - you reduce helmet drag with laminar flow and go very slightly faster, and this will have an infinitesimal extra cooling effect. But its very doubtful that will outweigh the added "mixing" of turbulent flow - meaning that your head just gets to meet more cool air.

Your head is not a nuclear reactor; the air cooling you is not being forced through a high pressure pipe.

We all know closet hates helmets. He will be for any argument against them...

Not true, helmets do serve a function.

What I hate is when "Helmeteers" claim a function beyond their limitations and those that claim riding a bike is more dangerous than it is.

"Helmeteers" who claim one can be cooler wearing a helmet than not just kinda bugs me. It's just a sales ploy designed to prey on the ignorant and gullible.

Gee, I guess I had better go tell all those engineers designing nuclear reactors for the navy and civilian power plants that they screwed up.

No, I did not just make that up. In a closed system, as I said, the energy transfer within the fluid is higher for a finite time until the system reaches equilibrium. But your head is not not in a closed system. It has a constant flow of new fluid across it which maintains the fluid temperature that is in contact with your head and a higher temperature differential across the boundary. If you introduce turbulent flow, you reduce the overall flow rate over the head and thereby reduce the temperature differential across the boundary.

For this situation, the only function that matters is the energy transfer across the boundary and not the energy transfer from mixing within the fluid.

I was never talking about a closed system. Here is an example for a flat plate in a forced flow. The y axis is showing you ratio of turbulent flow plate temperature divided by laminar flow plate temperature. As you can see it never goes to 1. Depending on Reynolds number, turbulent flow is always many times cooler than laminar flow. I still cannot imagine a situation where it is otherwise, and you haven't actually provided any examples.

http://img263.imageshack.us/img263/4305/temperaturea.jpg

Convective cooling of a thin flat plate in laminar and turbulent flows Original Research Article
International Journal of Heat and Mass Transfer, Volume 33, Issue 3, March 1990, Pages 543-554
A. Vallejo, C. Trevin˜o (http://www.sciencedirect.com/science?_ob=GatewayURL&_method=citationSearch&_uoikey=B6V3H-481MTB1-14S&_origin=SDEMFRHTML&_version=1&md5=c57614443576f3b3e1d7497611fba766)

Any thread with the word "helmet" in the title is always entertaining.

This is not a real world choice.

The question is if a helmet is 'better' (cooler, warmer, more shade) than wearing the type of hat worn under conditions to keep one cooler or warmer and/or sun protection.

For a purpose specific hat vs. a helmet the answer is always that a helmet is never better.

This is not a real world choice.

AS has been obvious from the first post, numerous not real world "arguments" are made extolling the benefits, advantages and virtues of bicycle helmets.


Not true, helmets do serve a function.
What I hate is when "Helmeteers" claim a function beyond their limitations and those that claim riding a bike is more dangerous than it is.
"Helmeteers" who claim one can be cooler wearing a helmet than not just kinda bugs me. It's just a sales ploy designed to prey on the ignorant and gullible.

See Post #2. http://www.bikeforums.net/showthread.php/716348-Do-helmets-really-keep-you-(your-head)-COOLER?p=12288304&viewfull=1#post12288304

I was never talking about a closed system. Here is an example for a flat plate in a forced flow. The y axis is showing you ratio of turbulent flow plate temperature divided by laminar flow plate temperature. As you can see it never goes to 1. Depending on Reynolds number, turbulent flow is always many times cooler than laminar flow. I still cannot imagine a situation where it is otherwise, and you haven't actually provided any examples.

It's simple to understand why, if you actually know what laminar flow is - it's a flow pattern where air stays in layers. So the helmet would only be touched by a very small number of passing air molecules, which would mean little heat could be removed. In turbulent flow the air molecules bounce around, so far more of them would touch the helmet and more heat would be removed.

What I hate is when "Helmeteers" claim a function beyond their limitations and those that claim riding a bike is more dangerous than it is.

"Helmeteers" who claim one can be cooler wearing a helmet than not just kinda bugs me. It's just a sales ploy designed to prey on the ignorant and gullible.

HELMETEERS -- I love it! Stealin' that one, closet!

I'm picturing a geeky bunch of jersey-clad 'Power Rangers' who, in a flurry of pseudo-martial-arts moves, fling Wal-Mart helmets at 'errant' riders.

It's simple to understand why, if you actually know what laminar flow is - it's a flow pattern where air stays in layers. So the helmet would only be touched by a very small number of passing air molecules, which would mean little heat could be removed. In turbulent flow the air molecules bounce around, so far more of them would touch the helmet and more heat would be removed.No it is not quite that simple. And nice graph 'Dan The Man', but it does not replicate what is going on within a helmet. Let me try explaining it a different way since you guys are not looking at the other parameters.

The helmet is designed to create a laminar flow across the interior helmet surface. The air flow across the skin of a bald cyclist or through the hair of other cyclist may be some variation between laminar or turbulent flow, but it is not relevent to the air flow across the helmet interior surface. By creating laminar flow across the helmet interior surface, the air pressure within the helmet to head airspace is lowered over a helmet that produces turbulent flow within the entire airspace. The lower pressure within the laminar flow helmet allows a much greater volume of air to flow through the helmet. A higher pressure in the helmet airspace of the turbulent flow helmet would force more of the available air to flow around (outside the helmet). It is the greater volume of air flowing through the laminar flow helmet that creates the greater cooling.

On hot (>90) days I don't think I've ever noticed my head being too warm while cycling with a helmet except when stopped at red lights or climbing long steeper grade hills in full sun.

On warm days (70's) a helmet can make ones head feel a bit warmer than none, but it is relative, not an issue.

Kind of like how a t-shirt makes one feel a bit warmer when it is in the 70s, but is appreciated when it is 100F full sun.

No it is not quite that simple. And nice graph 'Dan The Man', but it does not replicate what is going on within a helmet. Let me try explaining it a different way since you guys are not looking at the other parameters.

The helmet is designed to create a laminar flow across the interior helmet surface. The air flow across the skin of a bald cyclist or through the hair of other cyclist may be some variation between laminar or turbulent flow, but it is not relevent to the air flow across the helmet interior surface. By creating laminar flow across the helmet interior surface, the air pressure within the helmet to head airspace is lowered over a helmet that produces turbulent flow within the entire airspace. The lower pressure within the laminar flow helmet allows a much greater volume of air to flow through the helmet. A higher pressure in the helmet airspace of the turbulent flow helmet would force more of the available air to flow around (outside the helmet). It is the greater volume of air flowing through the laminar flow helmet that creates the greater cooling.

You're talking about flow inside the helmet? Sorry: I missed that. I was thinking of the need to cool the helmet itself, to prevent it baking the head.

As for flow inside the helmet - I really don't believe that any manufacturer could guarantee laminar flow inside! Not unless they're allow to specify the exact skull shape of the wearer and how his/her hair is arranged (bald would be best.) Using google I can find a multitude of references to helmets with external laminar flow, but none for internal. Where did you get this idea from???

I thought that [that the top of the head is a major hot spot] was debunked a few years ago in the British Medical Journal.I don't think so. They may have debunked the crazy but popular notion that 75% of the heat of your body is lost via your head or something along those lines, but even so -- it gets hot, and it's a big part of your body, so a significant part of your body's heat will be lost there -- that's real. It's just not 75%.

If your helmet doesn't impact the airflow around your head much, and provides shade -- then I would expect it to help your head stay cooler. Without the shade factor (cloudy day?) I would not expect it to help, but the amount it hurts could be minimized by not affecting the airflow much.

I imagine helmet could be designed to be an air-scoop that funnels air past your head even faster than you are riding, but such a helmet would look ridiculous and would cause considerable drag. If currently available helmets do that, they do it on a very small scale -- in general, I'd expect them to hurt airflow more than they help -- but again, the shade is a nice bonus.

http://tiger.towson.edu/~cremus1/ebus311/beerhelmet.jpg

Cooler without in my experience, at least when it counts. Climbing in the hot sun I really would rather not have a helmet on my head, all it seems to do is insulate and keep my head extra sweaty.

As for flow inside the helmet - I really don't believe that any manufacturer could guarantee laminar flow inside! Not unless they're allow to specify the exact skull shape of the wearer and how his/her hair is arranged (bald would be best.) ... , but none for internal. Where did you get this idea from???Bell helmet rep in 1995. I have not seen any of their research data that either proves or disproves the idea. And I do not have the money to run a full system research study myself. But they did want to make helmets cooler to encourage more pro racers to wear them for obvious reasons.


Using google I can find a multitude of references to helmets with external laminar flow,Are those references more along the lines of laminar flow for less drag, as in time trial helmets, rather than better cooling.


I was thinking of the need to cool the helmet itself, to prevent it baking the head. OK, I can agree with your post for external air flow.