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Philip's Ravings

Choosing a Motorcycle Helmet

Rating: 4 votes, 4.25 average.

Rather like emergency braking, a discussion on helmets can be like a discussion on religion. People often take polarised views. Unlike emergency braking you don't really want to practice coming off your bike and having head impacts to test which is the best kind of helmet for you.

So short of repeated practical experience you have to learn a little bit about helmets to help you make a choice that is only like to be tested once.

One thing you'll notice when helmet shopping is there is a huge variation in price. One thing is certain - there is no correlation between price and protection.
Factors that can affect the price of a helmet (other than protection) include electronics, being light weight, pinlock visors, brand, breath guards, noise insulation, etc.

Another thing that is certain - there is no perfect helmet. A helmet manufacturer decides what kind of accidents they want to protect against and designs their helmet to limit the risks for those kinds of accidents. And often being good in one area implies a helmet wont be so good in another, as their are often trade offs involved.

One important thing to note is that most developed countries (including New Zealand) don't permit a motorcycle helmet for public road use to be sold unless it meets some well known standard. As a result, you can not buy an "unsafe" helmet.

What do you want a helmet for?

This might sound like a dumb question, but it is very important. For example, some riders spend most of their time in 50km/h urban zones, some spend most of their time on open roads, while others only visit the track.
Why do I mention this? Because it affects the likely impact speeds your head is going to be involved in - which affects the material you want the outer shell of your helmet to be made out of, and how many 'G' forces your going to want your helmet to cope with.

Another thing you need to consider is how concerned you are about hard head impacts (as helmet designers often have to make concessions to make helmets capable of standing really hard hits). For example, do the areas you ride a lot in have a lot of road furniture around corners (bus stops, power poles, etc), so you are concerned about having your head rammed into something like this, or are you more worried about having a slide and then a "soft" impact (perhaps hitting a curb for example after your jacket and pants have scrubbed off some of your speed).

How a Helmet Works

Helmets have two main parts to them that are designed to protect you. An outer hard shell, and then an inner energy absorbing foam.

The hard outer shell is designed to prevent something penetrating the helmet and entering your head, and also to dissipate the initial impact energy by dispersing as much as it can around the outside of the shell.

The inner energy absorbing foam is their to absorb as much of the impact energy as possible without transferring it into your head and brain. It does this by compressing. It can only compress once.

One thing that is really important with a helmet is a tight fit. Let me repeat that because it is so critical. A helmet should be a tight fit. The reason this is so critical is you do not want your head bouncing around inside the helmet during the impact. If something has to have a 100km/h impact speed, let it be the outer shell of the helmet, and not your "unprotected" head against the inner shell of the helmet.

One important thing you should note - the materials used in the helmet break down with time. You just can't tell when the inner energy absorbing foam (which you can't usually see) has lost a critical amount of that energy absorbing quality. Also the foam can break down in the presence of petroleum based chemicals, such as paint, petrol, glues, etc (so be careful were you store a helmet).
Most helmet manufacturers recommend that you replace helmets every 2 to 5 years because of this.

Also note that the energy absorbing foam is a "single use" item (in much the same way you can only detonate a grenade once). Once it compresses once that's it. That's one of the main reasons why if you have an accident you have to throw the helmet away.
It is also why you must be very careful not to drop a helmet onto a hard surface. You can not visually inspect the foam. There is just no safe way to tell if the foam has partially compressed.
Put it this way. Say you had a grenade with a 7s fuse. You knocked the pin out by accident and quickly put it back in again. Would you want to risk using that single use grenade now that your not quite sure how long the fuse is?

Types of helmets
There are four main materials used for the outer shell of a helmet.

Plastic: Compared to the other types of outer shell material plastic is relatively soft. They sometimes even breakup during impacts. In my personal opinion plastic shell helmets are particularly good at low speed (50km/h) soft impacts. In my opinion, this is because the plastic tends to flex a lot, causing it to absorb a lot of energy. And you should not take concern over the potential issue of the helmet cracking in an impact. Would you rather a helmet cracked because of the amount of energy it had absorbed, or you head because the helmet has a super strong shell and transferred so many 'G' forces into your skull that it cracked instead?

Polycarbonate: Polycarbonate is a bit like plastic, but much stronger while still retaining the flexing characteristics of plastic. As a result, the outer shell can absorb a lot of the impact energy before transferring it into the inner foam.

Fibreglass: Fibreglass helmets tend to be very hard. They are capable of sustaining a considerable impact. However they don't tend to flex. In my opinion, as a result, they have to rely on the internal energy absorbing foam and as a result they tend to transfer more energy into your brain. In my opinion, the harder shells are more suitable for higher speed accidents (such as 100km/h).

Carbon Fibre: Carbon fibre helmets are like Firebglass helmets, but harder still and even more rigid (aka, even more energy transfer into the inside of the helmet). Because these helmets are super hard I personally believe they are well suited to high speed track use, or people concerned about really hard impacts to the head, or hard double impacts. My personal belief is that by making this choice you are accepting that more energy is going to be transferred to your brain (more about this later in the standards).

Composite: Composite helmets (made from a resin/fiber mix such as fiberglass, carbon fiber and/or Kevlar) are the toughest to talk about. Effectively the manufacturer can choose the flex and energy transfer characteristics. So for the kind of accidents a manufacturer is trying to target they can choose the optimal parameters. Is that the same kind of accident you are worried about? Who knows. In my personal opinion, polycarbonate helmets can offer the best of everything. You need to give some consideration to the testing standard results (below) to work out it is is going to suit you.

Helmet Standards

Also known as the Department of Transportation’s Federal Motor Vehicle Safety Standard No. 218. Although a very mature standard (first issued in 1974) the DOT standard is often considered the baseline (or should I say minimum requirement) for helmet protection. However don't let this fool you into believing that a helmet that only has a DOT certification is in some way inferior. In deed, some people believe that the DOT standard is superior for certain types of accidents.

Some criticism has been raised over DOT being a self certified system. It is up to the manufacturer to decide if their helmet meets the DOT standard, and if they feel it does, they can proclaim the fact. There is also no requirement for ongoing testing of helmets rolling off the production line.

SNELL: The Snell Foundation has a number of standards that have evolved over time, usually named after the year the revision was released in, such as M2000, M2005 and M2010. I'll be blunt, I am not a fan of the SNELL standards.

Way back when the Snell Foundation was formed they had to differentiate themselves from the DOT standard. One of the things they did was to include in the test an incredibly hard double impact test on the helmet. A test I personally don't think you'll likely to see that often in real life (aka, a rapid hard double impact to the same spot on the helmet).

The helmet manufacturers responded by making helmets with a super hard shell. Fibreglass and then Carbon fibre helmets started appearing. However there was a downside. These super hard shells didn't flex. The result was that more of the impact energy was transmitted into the energy absorbing foam in the helmet and then into the riders skull.
Snell specified that energy transfer to the brain was to be limited to 300g. The problem is a lot of people (including myself) don't believe the brain can sustain a 300g impact. In fact, many people consider anything from 300g and above to be fatal.

So now you have these super hard helmets with the Snell sticker that can leave you a vegetable (or dead) if you do suffer a hard hit.

Other people such as the Europeans believed the danger was so great they legislated that the energy transfer has to be limited to 275g (known as ECE 22-05). Even 275g is high, but it is safer on the brain than 300g. You are more likely to get a non-permanent brain injury than a permanent brain injury.
A lot of the ECE 22-05 helmets are made from a softer material, so that the outer shell can flex, hence reducing the amount of energy the inner foam has to absorb.

The Snell Foundation get around 50c from every sticker that a manufacturer puts on a Snell tested helmet. Snell suddenly lost all of the revenue from helmets being sold in Europe. So finally in 2010 Snell revised their "standard". It is called Snell 2010, and it now stipulates the the energy transfer is to be limited to 275g. Now the stickers can go back on the helmets being sold in Europe.
The cynic in me says that Snell did this purely to get the revenue back, as opposed to suddenly deciding the 300g limit that they had previously used was no longer safe.

You can read more about the M2010 variant of the Snell standard here:

You can read a famous scathing appraisal of the SNELL tests here:

ECE 22-05: ECE 22-05 is a European helmet standard, and is a legal requirement in around 50 countries. As a result a lot of helmets are made to this standard (especially helmets manufactured in Europe). ECE 22-05 is almost a complimentary standard to DOT, and the vast majority of helmets that pass the ECE 22-05 standard would also meet the DOT standard.

Unlike DOT, ECE 22-05 mandates compulsory batch testing of helmets coming off the production line.

ECE 22-05 limits the amount of energy that can be transferred into your brain to 275g.

SHARP: SHARP is a UK Government initiative to provide an independent way of comparing the protection offered by helmets. It is not a test standard. SHARP gives helmets a 1 to 5 (5 being the best) rating so you can see how much more protection one type of helmet offers over another.

SHARP document on their web site the overall testing methodology on their web site, but don't give specifics. As a result some people discredit the SHARP system because the results can not be independently verified. However on the whole the SHARP comparative ratings are well regarded and I personally consider them to be a valuable source of information and would strongly recommend checking the SHARP score of any helmet being purchased.

I personally support the SHARP test rating system. The issue with just having a test standard such as ECE 22-05 is that it does not reward manufacturers who want to make a helmet that exceeds the standard. Consumers simply can not tell by reading marketing material how much brand "x" of helmet exceeds a set standard compared to brand "y".

SHARP helmet testing results are available for public viewing at the SHARP web site:


Because you can not buy a motorcycle helmet for use on a public road that does not meet a well known standard your first concern should not be picking a helmet made to a particular standard, but to choosing a helmet this is a tight (yet comfortable) fit.

Personally I then look for a helmet that meets the ECE 22-05 standard (and most helmets do).

And then I look for a helmet with a 4 or 5 star SHARP rating.

And then lastly consider the extras that you want, such as:
* Helmet weight
* Visor options, such as pinlock, half tint, etc.
* Electronics blue tooth or an intercom
* Noise insulation
* Price

If you follow these guidelines then can rest assured you have done all that you can reasonably do to choose a helmet that offers you a good degree of protection.

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  1. rustic101's Avatar
    Very good reading and should bode well with some readers. While a heavy helmet I love my N103 Ncom.
  2. R-Soul's Avatar
    Great article! Blings in the post.

    I do wonder though, how many secondary or even primary injuries are caused by heavy helmets wrenching spinal columns and necks?

    Just going by my own commonsense, it seems to me that weight MUST play an important factor in rider safety. After all, hitting a pole/kerb at 80km/hr will cause quite abit of whiplash to the neck.

    Also, the Laser super skin seems to highlight differenttypes of injuries caused by a part of the helmet getting caught against whatever ithits, and the rotation caused by this friction apperas to be major contributor to brain damage (although I am not sure what the major causes of head injury are).

    It would be an interesting excercse to do some research on this.

  3. sinned's Avatar
    A useful reference - thanks for the effort.
  4. Spearfish's Avatar
    Great work, to be honest I didn't give much thought to the helmet at the time other than fit and cost, probably common to new riders.
    Your article is food for thought, Thanks!
  5. Biggles08's Avatar
    Good article and well written. I have only recently become interested in the Sharp rating system since gaining a new sponsor 'CABERG helmets.' These all have 5 star ratings, even the 'flip top' helmet they have. I wear one on the track racing and find the fit to be great for my head shape. Previously I wore a Shoei XR1000 which I loved too. Incidentally, although a 'big brand,' the XR1000 helmet only got a 3 star SHARP rating which surprised me!
  6. rocketman1's Avatar
    I have KBC , But looking at the Sharp Rating it only got a 2.
    I was off around the Coro loop the next day, so decided to invest in a 4-5 rated helmet.
    I wandered all over Hamilton bike shops, back and forward finally found an AGV at Waikato Yamaha, rated 4 , felt great , had it 6 months now, & love it, Quiet, Light, Resin.
    It got a bit of flash Rossi design on it, but keeps an ol bugger like me young.
  7. CUTE4U's Avatar
    Fab article , very informative and a great read. Excellent points on knowing what is the right Helmet to suit your riding.