Until very recently, helmets have had two jobs: keep things from impaling your head and reduce the force of hitting things that hit it. Two companies unveiled street helmets at the AIMExpo show this year that take things one massively important step further—to protect your brain, as well as your skull.

As we’ve stated in other articles, the purpose of wearing a helmet is to protect your head. But almost all helmets on the market today focus primarily on protecting the skull itself and seem to forget about what’s inside it.

If you read our helmet explainer, you learned about the various safety standards (both optional and mandatory) in various parts of the world. Wes and I are actually not huge fans of the SNELL standard because, while it does add some nice restraints onto the DOT standard’s testing, it puts the brain even further away from the skull in terms of importance. The stiffer EPS liner on SNELL helmets is meant to keep your skull from cracking under even more severe impacts, but doing so makes it more susceptible to causing brain injuries at lesser, more common impacts.

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Our coverage of the importance of the Bell Flex Liner in the new Bell Pro Star was met with so much suspicion that I decided this needed its own post. Let’s dive in.

Current Testing

Both DOT and SNELL are aimed at measuring and regulating the amount of linear acceleration translated to the head, which is measured in G’s. The SNELL standard is more severe, as its initial test drops the helmet from 7.5 meters over the DOT’s six meter drop.

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When I was at the Arai Corsair X launch, one of the Arai staff commented that the DOT drop accelerates the helmet up to a velocity of about 14 miles per hour, which wasn’t nearly sufficient enough protection for motorcycle speeds often four and five times as fast. This surprised me, because that’s not exactly what those numbers mean.

I spoke with Bell Helmet’s head of testing, Alex Szela, to get an expert’s take. He told me that the standards were designed with testing data about the severity of the impacts needed at normal speeds to fracture the skull. The test uses a six meter drop, which accelerates the helmet to 14 miles per hour before striking an anvil, which brings the helmet to a complete stop instantly. They do this not because you’re going to fall from six feet at that speed, but because that test transfers the same amount of energy to the head form as a normal, catastrophic accident.

This graph was included in a SNELL presentation at AIMExpo last year, and is intended to make you think that SNELL helmets are better because they protect the head better at drops from six meters/second (the DOT standard) or more.

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While that’s true, and great, what they don’t mention is that a human who takes the force represented in an 8 m/s or 10 m/s impact is also dead, given the forces transferred. Also, notice that in drops under 6 m/s, the type you’re much more likely to have, the SNELL helmet is actually slightly worse.

Let’s Look At Some Graphs

The following are some graphics provided by 6D featuring their ODS (Omni Directional Suspension) system. 6D is a helmet company created out of the realization that helmets needed to focus more on brain protection.

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For those of you who missed the article on 6D’s new ATS street helmet, the ODS system connects two EPS layers with 54 elastomeric isolation dampers, which look like little rubber suction cups. This system allows the two layers to move independently and act sort of like a damper in a suspension system, slowing the head down as it rotates on impact - which is what causes the brain to spin inside the skull and causes brain injuries.

(A bit of a disclaimer: Let me first say the following information was created around the 6D ATR dirt helmet. The numbers are not the same as their upcoming street helmet, but the differences between those and other street helmets will be similar to the differences between the 6D dirt helmet and other dirt helmets. The data for the Snell/DOT and ECE helmets comes from an average of all the helmets tested.)

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This first graph, like most that follow, looks more confusing at first glance than it really is. This test is the same test done in the standard DOT test with a helmet loaded with a head form dropped on a flat anvil, except it only shows drops from heights less than the standard (because why give the competition your standard’s test data, right?)

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This test shows the linear acceleration, which is measured in G’s, felt by the head form at various heights.


Notice that, with each test, the 6D helmet with the ODS system translates significantly less acceleration - especially important when you consider that concussions start occurring at or above 60 G’s.


This test is similar to the last one but, instead of the helmet hitting dead on, the helmet hits an incline anvil. And, as with the last test, it’s designed to measure linear acceleration (what most tests are looking for) when hit at two different speeds at various points on the helmet.

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The 6D isn’t able to keep the impacts out of concussion levels at the full speed DOT drop, but it is significantly lower than the helmets without it.


This test is similar to the last one, but its focus is on measuring angular acceleration rather than linear acceleration, which is measured in radians per second squared (which is a fancy way of saying how fast we accelerate). This is measured with an angular drop onto an angular anvil, and is designed to simulate the most common type of crash and measure how much the helmet form rotates inside the helmet.

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Bob Weber, CEO of 6D, told me that the real risk of rupture or concussions come in at about the 3.5 krad/s range, and is pretty much done for once in the 6 krad/s range. It’s pretty scary how much risk we’re at in some of these helmets even in lesser hits.


Another thing the guys at 6D noticed was that, while not the intended effect of the ODS system, the helmets helped to act like the rebound in a suspension system to slow the force of the impact. The graphs above show a low and high velocity impact, and how the 6D takes vastly longer to transfer that energy to the head form. Think of it as someone hitting you hard versus shoving you hard. The force is the same, but slower that force is applied, the less damage it does.

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If you think about it, we measure so much of this data in force over time that while most helmets focus on reducing the force, this one reduces the force and elongates the time—essentially working to our benefit at both sides of the equation.

This Is Brand New Territory

The one thing I think it’s important to realize is that this is a brand new way of looking at helmet safety. Both Bell and 6D were hesitant to answer my questions because they both realize there is no great way to measure what the brain is doing inside the skull well.

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We can see from autopsies and from brain scans post catastrophic injuries that these forces are at work and causing this trauma, but no one has a good system to measure it yet.

So, Bell and 6D are doing the best they can without any real way to prove they are succeeding at reducing the forces felt to the brain. They can measure the rotational forces applied to the head, as those correlate with the ones felt by the brain, and they can use that to point them in the right direction.

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All of the current safety standards were created with tons of data, both with baselines for the forces deemed acceptable version not, but also those from easily repeatable tests like the standard anvil drop. 6D and Bell are the only ones to do use inclined anvils this extensively, because both realize they better represent the types of hits actually experienced by motorcyclists.

If you have more questions, the 6D site has more videos and a ton of information from testing they’ve done. Yes, it was done by the company selling the products and no, it can’t be taken as gospel—but it’s a start to the education process, and maybe a different look at safety than has been done by everyone else.

Can brain protection in helmets be more than just vaporware, or another reason for helmet companies to charge you more? Hopefully so.