Here are more questions!

"Them"? Helmets or hats?

Do all hats have the same exact thermal properties? If hats, are you talking about people wearing them exercising? If hats, are you talking about people wearing them while travelling at 15 or so mph?

I'm sorry, no time to chat right now.

I realize this is a rhetorical question, but the answer is "yes, some do".

A straw hat or sombrero will keep your head cooler -- it does this by providing shade but being still porous enough to allow decent air flow as well.

If a helmet is designed to provide good shade but not restrict air flow much, it could help keep your head cooler. I don't recall ever seeing a bicycle helmet that didn't restrict air flow much (even with all the big air vents, which reduce the shade factor as well), but it could be done.

Yes, a helmet could provide enough extra shade but not restrict enough airflow to keep your head cooler. Any additional airflow restriction is made more moot by travelling at higher speeds.

The issue I find a problem with helmets is with sweat, which people might be interpreting as evidence of being "hotter". Of course, this is more of a issue when going up hill, where one is going slower with more exertion. In such a situation, a helmet might be hotter.

^ plus sweat doesn't evaporate through thick styrofoam. this is like how wool can be both cool and warm, because wool is porous and lets air conduct, but does also traps heat.

The main issue with helmets being "hotter" is that sweat will not evaporate quickly on contact points with thick styrofoam. There are vents but its not effective as having thousands (or maybe hundreds of thousands) of micro holes in a fabric. Conversely helmets and decreased sweat evaporation may even make your head colder in frigid temps (just like when you have a non breathable slicker on during winter and your sweat can't evaporate and you end up soaking yourself and getting colder).

I think thats the next tech in helmets... maybe a totally breathable helmet? Like something thats dense and has impact protection, but also is not totally rigid but still breathable.

All I can say is that I am inevitably much sweatier with a helmet than without. It's one reason I stopped wearing one... without it, I'm generally able to cycle to work in my work clothes, which is a lot less of a PITA.

If I'm rec cycling and concerned about heat, a wet bandana around the neck (carotid arteries) does far more than anything else. I believe it's a common survival tip. I learned it from Fresno roofers.

This is what I was getting at. For me, it seems this really only a problem in normal riding (ie, not hill climbing) on my forehead.

As far as dealing with heat a bicycle helmet is the least of my concerns. Mid summer I'd rather have one on (or a non floppy well ventilated hat) than none at all.

i hate that I have 3 helmets... and that every helmet after my first one I always thought to myself: "don't get a dark colored/black helmet... get something different lighter like grey or white... to avoid the heat absorption"....

all three of my helmets are black... sometimes those sales on bonktown induce temporary amnesia...

Hm, yes, all very true about the wind flow if the helmet has the same frontal area as your forehead, it however does not.

If you guys think not wearing a hat under the summer sun doesn't keep you cool then you've got some ulterior motives.

That wouldn't surprise me.

I think that not wearing a hat under the summer sun doesn't keep me cool.
Not sure of my motives though, just plain experience.

Good job, 5 response post in a row, ALL over a month late.

Not as "good" as the irrelevant discussion about laminar flow in helmet! That's really hard to top!

Yap, yap, yap.

I'm thin enough on top that it's a concern, not least because getting sunburned on the top of my head is no fun and having a criss-cross pattern of sunburn seems like even less fun.

I fold a handkerchief and use it to line my helmet when I'm cycling in the sun. Gives me the protection of the helmet while keeping the sun off my head. It's not so great for keeping cool though, by the end of a ride in the summer I can usually wring the sweat out of the handkerchief.

more vents = cooler head... Imagine wearing a motorcycle helmet while biking... no vents = super hot... more vents = better

But arguably less protection. Some studies have indicated more vents (especially of the style most bike helmets use) may increase rotational injury (since the vents are more prone to "grab"). If we are wearing a helmet for safety, the best kind are usually the "skate-style" helmets with no or few vents. If you aren't concerned about safety enough to go with the more ineffective, and possibly unproductive kind, why wear one at all?

don't forget that the failure rate for these new helmets with larger vents is greater.

Helmets still have to pass the same certification test with less foam, so the foam had to be altered. Helmets that pass the tests are harder and break more readily than the older designs that had more foam that broke apart less often.

Then again, to most people a helmet breaking often reassures them that the helmet saved their life, so maybe a helmet that is less protective may be also be more often perceived as providing more protection. A replacement purchase racks up another sale for the company too and perhaps even raises more sales as those who's helmet has broken tell the tale of how the helmet saved them, even if all it did was fail by breaking and not compressing (which is how these things are supposed to work).

A true life expiriment. Closet and other anti helmet crowd claims that if a helmet breaks it did nothing. Try this. Take an empty styofoam coffee cup. (make that an empty cup--sure dont want EPA nazis getting upset) Push down on it. It will give (that means taking up energy) and then will finally break. Since it took up energy before it broke it is doing its job. A broken helmet does the same thing.

Btw as I have posted before I personally feel cooler with a helmet--mine is white and well vented with a visor. Also it does provide some shade for my ears from the sun. A helmet could even provide some protecton fron skin cancer.

You can lead a horse to water, but you just can't make it drink.

That's not true. A broken helmet fattens the profit of helmet manufacturers if the cyclist believes a helmet is worth the cash because that cyclist will line up at the counter to buy a new one

not quite. Eps is supposed to deflect energy by compressing, not splitting. Splitting can occur after the maximum compression has occurred, or if the foam fails in it's compression. Once the EPS has split, it cannot provide any protection.

Records of helmet failure has increased with newer designs. Older designs had lower rates of failure.

Yes, it took some energy to compress it to the point that it would split, and then some more to actually split, and that's energy that didn't go into splitting your head. The question is if this is a significant amount of energy, and I don't recall ever seeing anybody actually measuring this.

Yes, if the helmet split, it failed. But the assertion that it provided no protection up until that point is unsupported as far as I know. Common sense (or simply my own educated guess, take your pick) tells me that it probably provided a little protection up until that point -- but not very much -- but I have no evidence of this either way. Do you?

It wouldn't be a difficult thing to test -- get some sensor-laden crash test dummies, and throw them around (in a controlled and repeatable way, of course) in such a way that their heads have harder impacts than bicycle helmets are designed to protect against. Repeat with and without helmet, at varying impact levels. Keep track of the condition of the helmet after each impact, as well as the sensor readings and the intensity and other details of the impact.

Common sense suggests to me that this is correct (simply due to the trend of adding more and more ventilation), but do you have any citations or other data to back this up?

Goes the dog!

This is silly, since it's based on speculative problems.

Anyway, all engineering involves compromises. Including the "skate style" helmets.

The issue is not that something manages not to be "perfect".

The issue is whether the benefits outweigh the costs (something that is "arguably" not established for the case of bicycle helmets).

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Is that true? It would not surprise me that the old hard-shell helmets had a lower "failure" rate but I wonder if there are significant differences for helmets made the same way (but with more or less vents).

well, that's a problem now, isn't it?

Manufacturers keep a close eye on this but don't want to give out information on it as it can reflect badly on the protective qualities of their product. Certainly we know it happens and manufacturers try to prevent it, but fail to do so. Letting people believe broken helmets are helmets that have "worked" works in their favor. Telling them that when a helmet splits, cracks, or comes apart the helmet isn't useful doesn't help them at all.

I've had a Bell representative tell me that a helmet splitting is a valid form of attenuating energy, which of course is technically true, but misleading in the extreme. Helmets work via compression, not by splitting.

Measurement rates of energy that coincides with the splitting of helmets is also extremely difficult to come by but we know at what rate of impact a helmet is tested to and that rate does not correspond to real life serious injury or death situations. Most conditions that result in such serious results are far beyond the limitations of helmets. Manufacturers are careful to say their product cannot be relied upon to prevent these types of injuries and that serious injury can occur to any wearer of their products by any impact.

Collisions, falls, and impacts to the head is an extremely complicated issue and not one that will be controlled by a single, simple, mitigating factor. Despite what emotion Helmeteers bring to the table, placing a helmet on a head does little to change much.