Ducati Monster Forum

How to solve the helmet hot spot (pressure point) problem

Some people are lucky.
“Helmet? Just about any manufacturer’s size M would fit me fine.”
I’ve heard (read) comment like that.
If you are one of those people, consider yourself being lucky.
I’m writing this for those who are feeling like 
“It’s virtually impossible to find the helmet that won’t give me a painful hot spot. Pretty much every helmet I have tried starts hurting after an hour or so ...”

I started wearing motorcycle helmet in the early 80s, and yes, in the past, I had always had hot spot problem, until I found out what was causing it.
Seriously, ill fitting helmet can make you feel like you are wearing medieval torture device.
Isn’t it nice if you can wear helmet for long hours continuously, without feeling pain, yet it (the helmet) doesn’t slip around on your head every time you do the head check?

(https://farm5.staticflickr.com/4462/37496604612_6f3ff1716b_b.jpg)


Know your head size and shape (not just “round, intermediate, long oval ...”)

“If you know the enemy and know yourself, you need not fear the result of a hundred battles. If you know yourself but not the enemy, for every victory gained you will also suffer a defeat. If you know neither the enemy nor yourself, you will succumb in every battle.”
― Sun Tzu(544BC - 496BC) , The Art of War


So, following one of the greatest strategist and philosopher, we are going to figure out about ourselves (our own head) and, ...
the enemy...  the helmet hot spot (what it really is, and how it happens).

The very first thing you need to do is to know your own head size and shape, before start looking at bunch of helmet reviews at Revzilla and Webbikeworld.

When you look at the user review of the helmet on the net, some people say Helmet XXX runs small and some say opposite, some say helmet ZZZ is narrow and some say it’s round. This happens because a lot (if not all) of them actually don’t know the “real” shape of their head.
Majority of the people just “think” they have intermediate oval / neutral shape head.
The word “intermediate” , “neutral” is a very slippery word.
Some are roundish, some are more oval-ish, some have bump, some have large flat area (usually forehead or the back of the head), all these small things can cause painful hot spot.

Now, rather than writing down the long and tedious generic theories about helmet fitting, I will use my own head as an example, to demonstrate how to get rid of the painful hot spot.
That way, you probably understand better “how to” solve the problem.


Taking measurement

So, take a tape measure, and measure your head circumference size, like a picture below.
But, everyone knows this already, right?
(https://cdn.shopify.com/s/files/1/0186/5388/files/HEAD_MEASUREMENT.jpg?790)

Note.
It is better to have someone to take a measurement, than trying to do by yourself.

Take a few measurement, and use the largest one.    

Next, take a measurement of your head, front to back, side to side, using something like this
 
(https://www.sculpturehouse.com/images/Product/large/aluminum_caliper_c12.jpg)

That's called sculpture’s caliper. You can find them at your local art supply store.

(In case you can't find it locally, here's one of the example where you can buy things like this.
https://www.sculpturehouse.com/p-21-sculptors-aluminum-caliper-12.aspx)

Alternatively, you can use the closet door (sliding door).  Lay down on the floor, place your head between the door and the frame.
(If you do this, be careful when to do it. Try not to be witnessed by your wife/husband, girlfriend/boyfriend. They may start worrying about you.)

Next, run your finger tips on your head, to see if there’s any irregular bumps, large flat area, corners, etc.
This step is very important.
In my own case, this is the main reason of having the hot spot even though I’m wearing the correct size, correct shaped helmet.


Head shape

These days, most everyone who sells the helmets knows that they come in different internal shapes.
(If they don’t know, or seems like they are not willing to spend some time with you, don’t buy from them.)

I assume, if you are reading this, you already did the homework and know about the basics,(long oval, intermediate oval, round, etc, etc), so I believe you are not trying to squeeze your long oval shaped head into the round helmet (or, the other way around.)
Thus, I’m not going to talk about those basic mistakes.
And, if you have the helmet with wrong internal shape, nothing really helps. You have to start with the helmet that has , at least, the internal shape that is close  to your head.

One thing I would like to talk about the head / helmet internal shape, is that the vagueness of the term, such as 
“long oval”, “intermediate”, etc.

Take a look at the picture below.

fig.1
(https://farm2.staticflickr.com/1851/43210897305_7c6d0165fa_b.jpg)

What people call “long oval head” is either “long elliptical” or “long sub-elliptical” head.

What referred as “intermediate” “neutral” is anywhere in between “elliptical” and “short-sub-elliptical”.

What called “round” is,... well, “spherical”.


Now, take a look at the measurement we took.


My own head measurements are

Circumference       56.5 cm
Width (Side to side)    17 cm
Length(Frond to back)   19 cm

Width (side-side) : length (front-back) ratio is 0.89 : 1. (I will talk about this later.)
Side to side measurement is about 10% shorter than front to back measurement.

Judging from these numbers,my head shape seems like so called “round-oval”.

The catch is, it is NOT.

 What these numbers don't tell you is that my head is pretty narrow at front(S size), the back side is a lot wider(M size or between M and L).
On top of that, my head has pointy corners at the top/back.

And that’s why lid-picker or helmet fitment data base on the internet (such as webbikeworld) never helped me.

Take a look at the picture below.

fig.2
(https://farm2.staticflickr.com/1849/30283275258_c79e6ba7b5_b.jpg)
fig.3
(https://farm2.staticflickr.com/1812/30283274968_edeee29346_b.jpg)


SO, my head at crown area (section X-X) is  a “short, short sub-elliptical” head.
Widest part of the head is closer to the back of the head, rather than in the middle (around the ears, temple area), front half is smaller than the rear half, narrow at forehead area, wider at the back.

However, at section Y-Y, near the top of my head, it ends with square-ish corners at each side.

Looking at from the back (section Z-Z), it looks like I have square shaped head at the top.

(Note: Keep in mind, the shape in the drawing is exaggerated so that you can see it clearly.)


So, these pointy corners at the back of my head start hurting after an hour or so, because some of the weight of the helmet is on these two “points”, rather than evenly spread over the large surface area.

And, if I go up one size larger helmet, wrongly thinking that the pain comes from “too tight” fitting helmet, things get worse.
Because with the loose fitting, the crown area can no longer support the weight of the helmet, and all of the weight will be on three points, on top of the head and two corners at the end.

fig.4
(https://farm2.staticflickr.com/1846/30283275468_5b5d269ac6_b.jpg)

As you can see, too small helmet would be pinching the side of my head, and it becomes a torture device after an hour or so.
(And if I get stuck in the heavy traffic, it really is a torture.)

Unfortunately, there aren’t many helmets with egg shaped (narrow at front, wide at the back) internal.
Even if I wear right size, typical “round-oval” helmet still gives me hot spot after 45min to 1 hour.

The solution is NOT to compress EPS liner with spoon, golf ball, or baseball bat, like some people do.
You need to change the thickness of the comfort liner padding.

fig. 5
(https://farm2.staticflickr.com/1838/30283274758_87635d6bbc_b.jpg)


... the end of part 1
    to be continued

  [popcorn]

Thanks - there are millions of riders who need this knowledge, but probably ~fourteen who bother to learn anything about it. I miss my previous Schuberth S1 Pro, molded on my head, but now they make intermediate and round helmets. My new S2 needs 10-15 mm foam padding on the sides.... They were known as the kings of long oval, but finally decided to make more money instead.

Thanks.
yeah, I hope this helps some people.
(It took me a lo OOO ng time to figure out this ... I seriously hope this can save some people's time and money ...)


Changing the thickness of the crown pad

Okay. Let’s take a look at fig. 5 in the last post again.

(https://farm2.staticflickr.com/1838/30283274758_87635d6bbc_b.jpg)

In order to reduce the pressure on those corners on the back / top of my head,
one thing I can do is to add more thickness to the back pad.
As you can see in the picture, this will move the head forward inside of the helmet.
Thus, creating more room at the back.

Most of the time, this is the first thing I would try.
(On my X-14 JDM (photo shown at the top of this thread, the one with fire unicorn on the side), replacing the back pad to thicker one, side pads to thinner ones are all I needed to get the correct fit.
Goes to show how important it is to start with the “right” internal shaped helmet. Also, I should note that, as of this writing, X-14’s liner system is one of the best design out there as far as adjustability (for fine tuning the fit) is concerned.
※ I will explain more about this later.)


Raising the helmet position

Another thing I can do is to raise the helmet, a little bit.
(and / or tilt the helmet forward / backward)

fig.6
(https://farm2.staticflickr.com/1814/44154394612_38bdaac465_b.jpg)


With Arai helmet, this is very easy to do.
Pull out the comfort liner, and adjust this tub.

photo.1 Helmet sits lowest with this setting
(https://farm2.staticflickr.com/1836/42395057850_ef66a1ab38_c.jpg)

photo.2 Helmet sits highest with this setting
(https://farm2.staticflickr.com/1848/30335299758_60410e0181_c.jpg)

Sometimes, raising the helmet position, or tweaking the tilt is all you need to get rid of the hot spot.
※ I will explain how to add foam to the comfort liner, etc , later




Now, does your hot spot problem sound like this?

1.The hot spot you feel pain / pressure is above your crown area.
eg: at the top end of forehead,  around hair line (or slightly above hair line)

2.The helmet feels nice and comfy, snug but not too tight, in the beginning of the ride.
But, at around 45 min. to 1 HR. mark, the pain starts kicking in, and it rapidly gets worse.


fig. 7
(https://farm2.staticflickr.com/1850/43296569075_c1f419bcb3_h.jpg)

Her skull shape is lightly drawn with blue pencil.
Blue pencil hatching area is where your head support the helmet most.
Do you have hot spot on cross hatched with red pencil area ?


Then, the cause of the hot spot is more of a “weight distribution”, rather than “tight fitting”.

Next time when you are out riding, and start feeling the pain, try this.

fig. 8
(https://farm2.staticflickr.com/1848/43297399895_8fb2e87dba_b.jpg)

Hold the bottom edge of the helmet, push it upward.
If you feel the pain / pressure momentarily going away, then, you know it’s the  “weight” that’s causing the pain.

“Slightly loose” fitting helmet, “not enough support around the cheek” helmet, “close but slightly off” internal shaped helmet,
can all cause this. Often, the front part sliding down as you keep riding.

...end of part 2
   to be continued

Great post! They should print this out and put it in every Cycle Gear shop. The very first helmet I bought from there ended up being too round for my head and gave me hot spots on my forehead. I used the less than ideal spoon trick to relieve it. When I got my 2nd helmet I must have tried over half a dozen ones before finding one that fit me perfectly (GT Air) although it still needed a smaller liner size. I wish manufactures gave better info about the shape and sizing of their helmets.

Let’s check out one more thing while we are talking about the helmet position on your head.

Go for a ride, after 45 minutes - 1 hour, look into the mirror.

How much space do you see between the eyebrow and eye port edge?

fig.9

(https://farm2.staticflickr.com/1890/29328727537_dcbc69425b_b.jpg)

When the helmet is worn properly, with modern day full face helmet, typically you should see about two-finger space between your eyebrow and the edge of the eye port.

If you look like fig.9 - A, chances are ...

You may be wearing too large helmet.

Your helmet may be slightly loose, or the fit is slightly off, it slips down on your forehead as you riding.

You may simply be wearing the helmet in a wrong way.

The thing is, it is possible that, even though the helmet is the right shape and the size, it can still sits too low on your head. (Depending on your skull structure and the helmet internal shape.)

To do the experiment (of the helmet height adjustment) is easy.
You can use just about any piece of foam that’s about the same size as your helmet’s center pad, with the thickness about 5 - 10 mm (it is not so important at this stage).
Or, if you don’t have a piece of foam handy, you can even use folded bandana for the experiment.

Once you know raising the helmet position makes difference, you can add some foam to the center pad.



This is how "SHOEI's personal fitting service" is done. (Sadly, this service is only available in Japan, and some euro countries. Not yet available in US.)

Take the measurement of your head, front to back, side to side, and circumference

(http://www.hansvanwijk.nl/wp-content/uploads/2016/11/shoei1.jpg)

Add some form, to where you need,

(http://bike7.jp/cmsdesigner/viewimg.php?entryname=topics1&entryid=01179&fileid=00000002&/%B5%A1%C7%BD.jpg&w=800)

(https://blog-001.west.edge.storage-yahoo.jp/res/blog-c0-dd/aim_the_1/folder/1527583/67/64719867/img_1?1382346845)

(https://blog-001.west.edge.storage-yahoo.jp/res/blog-c0-dd/aim_the_1/folder/1527583/67/64719867/img_2?1382346845)

(http://livedoor.blogimg.jp/ds_brog/imgs/1/b/1b2b463b-s.jpg)

Can you see where the extra foam is added?

(https://www.babel-blog.com/wp-content/uploads/2014/06/IMG_0943.jpg)

(https://blog-001.west.edge.storage-yahoo.jp/res/blog-c7-c7/jmhjs895/folder/128990/45/34259545/img_0?1375534037)

You get the idea how to work on the comfort liner?

You will need to add some foam around the hot spot (but NOT on the spot) to reduce the pressure to that point, (so that the pressure would be spread evenly, all across the head), NOT to depress the EPS liner in the hot spot area , or cutting off the foam(to make the foam padding thinner in the hot spot area), which, will make the matter worse.

You can find foam at local craft store, hardware store.
But if you want something more professional like result, buy open cell foam from the company like this.
That way, you can choose the foam with the thickness and the density you want.
https://www.foambymail.com/open-cell-foam.html


(https://www.foambymail.com/Merchant2/graphics/00000001/supermax1_540x404.jpg)
(https://www.foambymail.com/Merchant2/graphics/00000001/ss_hand_540x404.jpg)

As for adhesive, I recommend 3M super 77. (Available at your local art store, or industrial plastic store. It is also available from the link above.)
https://www.foambymail.com/3M/3m-super-77-spray-adhesive.html

(https://images.homedepot-static.com/productImages/5ea29b9b-8405-4907-bada-be6883c6d113/svn/3m-spray-adhesive-77-24voc30-64_1000.jpg)

BUT, don't use the glue until you are completely satisfied with the result.
Carry a small piece of foam and small leatherman with scissors and go for a test ride.
As you start feeling pain (or noticeable pressure point), stop, take off the helmet, cut the foam, add or subtract the thickness, and get back on riding. If you need, use (non permanent) double sided adhesive tape to hold the extra foam in place.

Repeat the test ride - fine tune with foam until you are satisfied.

... end of part 3
To be continued

How to check and adjust the fitment

So, how do you check the fitment?

Maybe you have tried the helmet at the store for 15 - 20 minutes before purchasing it, to make sure it won’t be too loose or too tight, yet, that helmet still gives you dreaded hot spot after an hour. You are now not so sure about the fitment.

Maybe you are in the market of the new helmet. You have narrowed down to two models, but can’t tell which one fits better. Trying them back and forth just confuses you more...

Or, you are in between the sizes. ( I am.) You tired both sizes, and still can’t decide which one to get.





In those situations, the simplest and the most effective way to figure out the fitting is,
to remove the cheek pads then try the helmet.

This will allow you to focus more on the crown area fitment.

The feeling of the cheek pads pressing against your face can give you the false sense of tight fitting helmet.
(Especially if you have ... err ... ample flesh on lower half your face...)

Fig. 10

(https://farm2.staticflickr.com/1865/43789900134_1e693bdb24_k.jpg)


Pay attention to the feeling around the crown area, and how the helmet is sitting on your head (height and angle).

If it’s sitting too low, and / or, if you feel the EPS linger pressed against your head above crown line, place something like folded bandana between the center pad and your head.
If it’s tilted down, place it slightly forward.

Check if it makes any difference.

Gently turn your head left - right, tilt up and down.

How does it feel, in the area cross hatched with red pencil, in the fig. 11?


Fig. 11

(https://farm2.staticflickr.com/1842/44465452372_6ab00e63d8_c.jpg) (https://flic.kr/p/2aKg4Qy)



Ideally, you should feel the red cross hatching area is "holding" your head with even, light pressure, rather than the helmet is clamping your head by a couple of "points".
With cheek pads removed, you shouldn’t feel any pressure point. (Because, the helmet is literally just sitting on your head, like crown.)
If you think you are feeling uneven pressure on your crown pad area with the cheek pads removed, you most probably need some adjustment.

(Before we go into how to add extra foam to the crown / center pad, just make sure you are not wearing too tight helmet.
Helmet is NOT a fashion item. I know a lot of people say, “ I don’t want to look like bobble head figure.” But, if you are thinking smaller helmet shell makes you look good, think again.
Watch the movie clip below. 0:45 - 0:54.

https://www.youtube.com/watch?v=zkNhzuTVqrg

That’s Vincent D’Onofrio wearing AGV AX-8 Evo, in “CHiPs" 2017 movie. And, look how big his face looks like.
If you wear too small helmet, when you open the face shield, your face will look awful and small shell makes your face look much bigger than it actually is.)

Okay, let’s get back to the subject.

(to be continued.)

This video shows (a little bit) about Arai’s fitting service.
Basically the same job as SHOEI’s Personal Fitting System.

The sponge work starts from 1:38.

https://youtu.be/8JMFqcO2zYI

https://www.youtube.com/watch?v=8JMFqcO2zYI&feature=youtu.be



Adding foam to the top and the back

(https://farm2.staticflickr.com/1860/43617930625_bde58752b0_o.jpg)

Left is original, adding extra layer of foam to the right side

(https://farm2.staticflickr.com/1869/44477040512_191ae8de7f_o.jpg)
(https://farm2.staticflickr.com/1867/43617934555_4b7f4d9433_o.jpg)


Arai RX-7-X comfort liner (stock), comes with two-layer removable sponge at the temple area.

(https://farm2.staticflickr.com/1865/43617934455_dff2e351ed_o.jpg)

SHOEI X-14 with added foam on top

(https://farm2.staticflickr.com/1847/30657188758_e2b1e3b183_o.jpg)[

Well, I’m in the middle of moving. (Which means, I have to pack up my drafting table, scanner and everything ...)
It will take a little while till I can post next one.

To be continued ...

The example

Dish washing sponge
(https://farm2.staticflickr.com/1897/43860955804_e2f66fc6e2_o.jpg)


Cut into half
(https://farm2.staticflickr.com/1893/44579423491_34d4d4e1ed_o.jpg)


Place on top of the head (between the center pad and EPS liner
(https://farm2.staticflickr.com/1852/43860955614_6cf64b2492_o.jpg)


But, that’s going to block air flow (of the top vent system). so ...

punch some holes through the sponge ...

(https://farm2.staticflickr.com/1894/43680490965_57795a819c_o.jpg)

(https://farm2.staticflickr.com/1899/42769615320_5d5fcbb0cd_o.jpg)


Done

(https://farm2.staticflickr.com/1887/44579423201_e942c70abe_o.jpg)

That’s good for the experiment, or temporally fix.
That sponge on top of your head may be good enough to be permanent fix in some cases.

If you need more fine tuning, here’s the basic guidelines. (what shape of foam, what density (hardness), where to put the foam)

(https://farm2.staticflickr.com/1855/44579418571_1f82c46ae6_b.jpg)


Adjust the top (helmet height) first.
Then, side (temple area),
forehead last.

If you want just a little bit less pressure in the certain area, instead of buying multiple different thickness and density foam,
you can punch hole(s) through the first layer of the sponge pad.
Punching holes makes the same effect as lowering the density (perforated area springs back less than solid part.)

You can find a punch set at your local craft store.
https://www.joann.com/realeather-mini-punch-set/10208106.html

(in my sketch, I drew a single big hole, which you can cut out with craft knife or sissors. But you may get better result with multiple small holes. It all depends on “how big the area you want to reduce the pressure”, “how tight the space is”,”how much pressure you want to reduce”, etc.)

Forehead pain explained
...and how to fix it

Let’s take a look at the two different shape of head.
They are, basically, both fall into the “long-oval” head category

Say, the size of these two heads are identical, front-back measurement are the same.
They both wear Arai Signet-X, in size M.

fig.13
(https://farm2.staticflickr.com/1866/44672769462_7013d6ab79_b.jpg)

After one hour of ride, despite the fact that both heads have the same front - back measurement and wearing the same helmet in the same size, one complains that his forehead hurts while the other is perfectly happy.
why and how did this happen?

Well, ...

Look at the size difference of cross hatching area (with red pencil) in the fig.13.

With the “narrow, pointy forehead” shape, the pressure on forehead area goes on very small area.
That hurts, after an hour or so.

With the “oval track shaped head”, the pressure is nicely spread across the larger surface area.
 

fig. 14
(https://farm2.staticflickr.com/1847/44672770242_8ab6b4a64c_c.jpg)

If you have protruded forehead, you may also have forehead pain problem.

fig.15

(https://farm2.staticflickr.com/1859/30851831548_6407a5c5a8_c.jpg)

When people have forehead pain, even with “supposed to be long - oval shaped helmet” (such as Arai Signet),
they simply think
“This helmet is not “long - oval” enough, too round for my head”.
“My head is probably too long for this helmet”
“Maybe the helmet is too small”

While in fact they are wearing the right size and right shaped (long - oval) helmet.
It’s just that, anything that’s pointy, protruding, WILL cause the pain, after some time.

(That said, the entire helmet industry is moving away from making extreme long - oval or real round shaped helmet.
Will talk more about it later.)


So, what can you do to solve this problem, then?

fig.16

(https://farm2.staticflickr.com/1852/44672769792_a450a6b463_c.jpg)

Option #1(left picture)

Using the leather punch, make some holes on the comfort liner front pad area.

Option #2(right picture)

Add some foam, like shown in the picture.

You can do both.

Basically, this is what you are trying to do.

fig.17
(https://farm2.staticflickr.com/1899/44672769192_e8ecde7572_c.jpg)




Next, I was originally going to explain about “pain on the temple area problem (round head rider’s problem)”.
but, there’s one more thing I need to explain before that.

Anatomy Lesson

Head shape classification

Anatomical terms for the three types of the head shapes (that we know as, Long oval, intermediate, and round)

Dolichocephalic (long head : what we call “long oval” head)

Brachycephalic (short head : what we call “ round head”)

Mesocephalic (intermediate)

The head shapes are classified by

Cephalic Index = x/y  ×  100
(CI = (bipareital diameter or BPD, side to side measurement) / (occipitofrontal diameter or OFD, front to back measurement) )  ×  100

FIg.18
click on the picture to see larger image

(https://farm2.staticflickr.com/1933/44200416725_86bcd3f919_o.jpg) (https://flic.kr/p/2akQFYr)Hot spot 18 (https://flic.kr/p/2akQFYr)  on Flickr


CI < 75 (female)  75.9 (male)     is Dolichocephalic
CI 75 to 83 (female) , 76 to 81 (male)       is Mesocephalic
CI > 83 (female), 81.1 (male)        is Brachycephalic

Note : There’s a difference between male and female skull. That's why the numbers are different.

What matters for the helmet fitment are

Smooth, more vertical frontal bone (forehead) on female skull

Male skull has more angled (tilted back) forehead

Rounded chin (female skull) vs Square chin (Male skull)

The more blocky and massive cranial mass on male skull vs rounder and tapering at the top female skull

Male skull have a deeper cranial structure



(I should probably explain the difference between caucasoid vs mongoloid skull shape, but let me keep on explaining about round head hot spot problem (pain on temple area) for now.)

(There’s also CRANIAL INDEX, which is essentially the same thing except for the fact that it uses the measurement taken from the skull.
For the people who deal with live human’s head (such as helmet manufacturers), Cephalic Index (which takes flesh and skin in account) is the one that matters.
For the people who deal with the skull (such as forensic artist), Cranial Index (which takes shrinkage of the dried bone in account) is the one to use.)

Now, this Cephalic Index would have been really useful if the helmet manufacturers had used this, to indicate the internal shape of their helmets.


Helmet for the round head

For example, Arai Quantum-X, supposed to be the most “round head friendly” helmet in U.S. market, would only work on the head with CI around 80 to 85.
I can tell, because my own head’s CI is 89, which is almost extreme end of Brachycephalic head, and Quantum-X is nowhere near as round head friendly as RX-7 -X (which is the JDM version of Corsair -X.)
If your head’s CI is greater than 85, even with Quantum-X (which Arai calls “round oval” helmet), you need to go one size up.

Instead of just saying “round-oval”, if Arai had said “Quantum-X ; round-oval shape, fits Cephalic Index 80 to 85”, it would have been much clearer. (Of course, they need to educate their potential customers, by explaining what Ci is. But, this will greatly reduce the hassle of buying a new helmet.)

AGV AX-8 Evo has egg shaped internal, and runs a little bit on the large side. But they have a lot thicker, plush crown pad in there.
The result is the helmet that works for the wide range of the head shape. (AGV GP-Tech was such a helmet also.)
I would say it (AX-8 Evo) works on the head with CI 75 to 85, even up to 90 so long as your forehead isn’t really wide.
(If you have wide, flat forehead and the CI is around 88 or over, it wouldn’t work.)



But, the hard, cold fact remains.
The true round head helmet is virtually non existent in today’s North American market.
NON of the helmet that are officially sold in US are designed for the head with CI greater than 85.

So, .... is there any option, other than going one size up, for the people who’s head CI more than 85?





Yes, there is.
Well, .... sort of.



... to be continued.

The CI is cool, but it took me several attempts with my head half way into a closet door to land at 75 - confirming my long oval.

I enjoyed my two Schuberths, R1 and SR1 Pro, but their new range are no longer long oval = unhappy with my S2 Sport. Could have enjoyed the Euro version of Signet (Quantum ST Pro), but it's discontinued. (EDIT: was out in 2017, seems to be back now) Curious about the Nexx XR2, but the company is struggling I think. BELL Star maybe... USA brands (Icon +?) without ECE certification (problematic here). Well, enough about me, other than to explain why I'm motivated to UNDERSTAND the situation.

There is no way that customers can do this as part of a normal buying procedure. Clumsy and too difficult to get accurate measurements. Dealers would have to do it for us. Yes, a few of us (less than 5%?) are troubled (=motivated) enough to understand and then solve the problems. Not enough to make us worthy of the extra effort. Dealers would like very much to NOT have to measure heads and spend time educating customers.

I have heard complaints, not many, but a few, and not one single time was it followed by a serious question about why, how or what can be done? Most riders endure their headache, hot spots, fatigue or whatever. I have even offered to test/analyze and custom fit their helmet, for free, but no, not interested. 'Been riding 30 years with more or less problem and pain, might as well continue....'  It's how we are...

  

Firs, let me show you  this rather interesting data.


Brand∙∙∙∙∙Model∙∙∙∙∙∙∙∙∙Market∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙internal width / internal length    × 100

Arai ∙∙∙∙∙Rapide SR ∙∙∙∙∙∙Japan ∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙86

SHOEI ∙∙∙X-14 ∙∙∙∙∙∙∙∙∙∙ Japan ∙∙∙∙∙∙∙∙∙∙∙∙∙∙stock 86 / with thinner side pads, thicker back pad  93

AGV ∙∙∙∙GP Tech ∙∙∙∙∙∙∙∙∙US∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙96

Schuberth∙∙C3 Pro ∙∙∙∙∙∙∙∙∙US∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙ 80

Arai∙∙∙∙∙∙RX-7-X ∙∙∙∙∙∙∙∙Japan∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙86

Arai ∙∙∙∙∙Quantum-X ∙∙∙∙∙∙∙US ∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙84

Suomy ∙∙∙SR Sport ∙∙∙∙∙∙∙∙∙US∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙78

Arai ∙∙∙∙∙RX-Q ∙∙∙∙∙∙∙∙∙∙∙∙US∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙77

AGV ∙∙∙∙AX-8 Evo ∙∙∙∙∙∙∙∙∙∙US ∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙94


Some of them are now getting pretty old.
However, you can see, Arai & SHOEI ‘s JDM helmets are designed and built for the CI 85+ type of head, and it hasn’t changed over time.

IF you know your CI, and it happens to be greater than 85, you will get a better, a lot better fit from JDM helmet.
(Most probably, you have been wearing one size bigger helmet, or suffering the painful hot spot. For example, I can wear helmet with width / length ratio 78 helmet, but it will hurt after an hour or so.)


Some interesting stuff you can learn from this info

RX-Q wasn’t really that “round” as some people believed.

C3Pro, while it is definitely not a long-oval helmet, it isn’t really round helmet at all, as some people believe.
(It’s just that they tend to run small, which means they are too short front - back for the size.)

Arai’s JDM full face has the most consistent width / length ratio over the decade (always around 85, 86).
With their center pad (crown pad) design, which has two layers of removable foam on the side,
You can change it to close to 90. (around 88, 89. If you still need more room at the side of the head after removing these peel-away sponge, you can use “leather punch” technique I described earlier. )

You can also change the center pad to thicker or thinner one.

SHOEI X-14 has the best liner system as far as the adjustability (for the different head shape) is concerned.
You can adjust it(JDM X-14)from 80 to 96. AND it’s very easy to do.

Very interestingly, AGV occasionally produce the helmet that works for the round head.
(But, the majority of their line up is not for the round head.)



So, the decision is up to you.

Anything you can try locally, it WON’T fit if your CI is more than 85. (Unless you go one size up.)
Anything you can buy from Revzilla / STG (so that you can return them easily) WON’T fit, either.

You know the helmets for the CI>85 head is available, but it has to come from the other side of pacific ocean.
There’s no way you can try them on before purchasing,
Even though you can return the item , exchange for different size  / model, you want to avoid that.

What to do?

Sending a detailed e-mail to the customer service of online vendor in Japan, telling them your CI and asking if this ZZZ helmet you’re interested would fit on your head will not help.
You only get reply that says to look at the manufacturer’s sizing chart.

... to be continued ....

About AGV AX-8 Evo

You can kinda tell, by looking at it from the bottom. (Actually, you can tell quite a bit by looking at the internal, once you study and learn about the helmet construction.)

AX-8 Evo (Naked)
(https://farm5.staticflickr.com/4358/36454847782_ece70b0876_b.jpg)

From left to right, C3 Pro, RX-7-X, GP Tech
(https://farm9.staticflickr.com/8136/29665538820_ba11a2770b_b.jpg)



Why AX-8 Evo works on “intermediate oval” head, despite the really round (or, should I say, “short sub elliptical (egg, or pear shaped)  internal.




#1 look at the cut out of eye port. How much of his forehead is exposed?

(https://farm2.staticflickr.com/1968/45246464102_95e33241e3_b.jpg)

(https://farm2.staticflickr.com/1962/30356811507_74a13ea8f3_z.jpg)

It’s cut higher, much higher than most of the full face helmet.

Incidentally, the same story applies to GP tech.

(https://farm2.staticflickr.com/1922/44573612864_147b5cb024_b.jpg)

(https://farm2.staticflickr.com/1978/44383418715_cb832f8a20_z.jpg)

Can you tell ?


With these helmet, the part of your forehead that typically gets hot spot does not come in contact with the helmet liner !





#2 Incredibly thick comfort liner padding

Well, I have to take the helmet out and measure, to give you the precise number, but it’s around full 1 inch thick on these AGV, as opposed to Arai / SHOEI’s  7- 9 mm.

Wearing these AGVs is kinda like this.

(https://farm2.staticflickr.com/1914/30356811687_70aaf3500e_b.jpg)

You don’t feel the EPS liner at all, because the padding so thick and puffy.


Wearing RX-7, X-14 is like this.

(https://farm2.staticflickr.com/1958/45246467022_4b31d0995e_b.jpg)

You (somewhat) feel the EPS liner, because of thin padding. Therefore, right shape, right fitting is way more critical on these helmet.


#3 About Revzilla’s review
Not trying to be a dick, but, Revzilla’s “round - long oval” rating is based on the customers feedback.
And almost all these customers never measured their head (which means they don’t know their true head shape).
So, they aren’t that accurate to begin with.


Please be patient, I will write about the "pain on one side of the head (AKA asymmetrical head syndrome)", soon.


It sounds like you have very similar problem to mine.  (Except for that your head CI is slightly greater than mine.)
Please be patient. I started explaining where / how to get round head helmet, and will continue.


Thanks for the feedback.
With CI 75 head, you have , on the surface, opposite problem, but essentially the same problem at the root.
Yes, the helmet manufacturers and the shop (authorized helmet dealers) really need to do more.

I don't think so.... they rate the helmets before they even go on sale. I guess they are rated by the staff - with or without manufacturer input...

Yes, but they change the rating over the time. I have seen some of the helmet "round - long oval" rating changed after some time.
Clearly, it is based on the customer feedback.

Some important tips about “how to choose size” when purchasing helmet from  overseas. (Meaning, you can’t “test fit” the helmet before placing an order.)

The untold story of fitment, shell size and liner thickness.

(I’m going to use round heads (CI ≧ 85) as an example here. But, what I’ll explain here applies to all type of head / helmet internal shape.)

Example story

(https://farm2.staticflickr.com/1974/45479395531_396e6383ca_b.jpg)

So, you are in between the sizes, S and M.
You have been advised  by people on the internet forums and by people at the local shop.
“Go for a smaller size, because the helmet (internal) will break in / stretch / mold onto your head.”

You believed that advice and purchased size Small instead of Medium.

You go for a ride happily with a brand new helmet ...

(https://farm2.staticflickr.com/1951/45437850012_ce194d3288_b.jpg)

 ... and  an hour later, you get unbearable pain on the side of your head ...

(https://farm2.staticflickr.com/1919/43727281160_bf3c51144b_b.jpg)




Sounds familiar?

If you have been riding many years already, tried more than a few different helmets and still get the hot spot on the same area, then you are either ...


wearing the wrong shaped helmet

wearing the wrong sized helmet

... or, could be doing both ...


You came across this thread, and measured your head’s front-back, side to side, and it turned out that you have CI 88 head.

So, now you know you have two problems.

The first problem is CI.
The helmets that you can buy locally, or from Revzilla, STG, etc, are all designed for the CI<85 head.

Knowing that JDM Arai / SHOEI are CI 85-86 helmet as a standard (can be tuned for higher CI), you decided to give it a shot.

But now, you are facing the second problem.

You are in between S and M size.

Which one should you order?

For obvious reason, you don’t want to end up ordering the wrong size and shipping it back to Japan, reordering the different size.

How do you decide the size when actually trying it on is not an option?

4-shell size vs 2-shell size helmet

Would you be surprised if I tell you that, with some helmet, the fitting is quite different from size to size?

???

Let’s take a look at two examples.

SHOEI X-14 VS OGK Kabuto RT-33

X-14  4-shell size

(https://farm2.staticflickr.com/1901/43726218700_dc1359d68a_z.jpg)

RT-33  2-shell size

(https://farm2.staticflickr.com/1956/43726219780_907db2e70d_q.jpg)

First, let’s take a look at X-14.
They come in 4 different shell sizes.
S(S and XS use the same shell), M, L, and XL (XL and XXL use the same shell).

fig. 19

(https://farm2.staticflickr.com/1950/45495997432_64c9f6ebc1_b.jpg)

The relationship between the shell, EPS liner, comfort liner, and the available inner space of the helmet is the same all across the sizes, except for XXL.

Except for XXL, all the helmet comes with 9mm thickness comfort liner as a standard, and you have options to go either thicker (+4mm) to make the fit tighter, or thinner (-4mm) to make the fit looser.

Each size of the helmet (except for XXL) has the same amount of tolerance / limitation for irregular bumps and slightly oversized head.

To put it simple, M is the scaled down copy of L, and S is the scaled down copy of M, they all have the same amount of space for fine tuning.




Now, RT-33, which comes in 2-shell size.

It uses the same shell for XS, S, and M. And  L, XL, XXL share the same, bigger sized shell.

Now, look at the picture below, pay particular attention to the liner thickness and the helmet labeled size.

fig. 20

(https://farm2.staticflickr.com/1972/43728899000_6ed4ec6025_b.jpg)


Yes, you guessed it right.

Size XS, S, and M are THE SAME HELMET with different thickness comfort liner installed.
And size L, XL, XXL are the same helmet, the difference is just the comfort liner thickness.

With this type of helmet, it is a little bit tricky to choose the size.

If you happen to be between the S and M size, you should order S, NOT M.

You have 15mm thick  foam surrounding your head, that’s a lot of cushioning, which will tolerate the slightly oversized  head (56.5 cm) without problem, even if your head some irregular bumps, bulges, etc.

BUT, if you are in between M and L, then, you’d better get L.

“Why? I don’t want a bigger shell size ! You just said “L” size helmet use the same shell as XL an XXL, that would make me looking like a bobble-head figure!!”

Well, I (sort of) understand the feeling, but take a look at the fig. 20 again.

RT-33 in size M comes with the 2nd  thinnest (9mm) comfort liner. (thinnest being 5mm on XXL).

Size M comes with the least amount of tolerance(extra space), besides XXL,  for irregular shapes and oversized head.

If your CI is 88 for example, and circumference is 58.5 cm, I can almost guarantee you that you are going to get painful hot spot on the side of your head if you wear size M.

IF. your head shape is slightly off (eg: CI 87, 88) BUT the correct size (between 57 and 58 cm), then M will work.

Or, if the head shape is correct (CI 85, 86) but circumference is slightly greater (58.5 cm), them M will work also.

However, when both the shape and the size are off at the same time, you can’t go for smaller size.

So, I hope you now understand the “multiple shell size” is NOT for the looks, but for function.

Also, I hope you understand now, that why some helmets cost more than the others.
(Just making 4 different sized molds for shell, and 5 different mold for EPS liner would easily make  X-14’s production cost more than twice the production cost of RT-33.)



Oh, by the way, the same rule applies for multiple shell sized helmet, when it comes to sizing.

If you happen to be in between the sizes, you can go for a smaller one
ONLY IF your CI is close enough(±1) to the helmet’s target CI.

Otherwise, you’d better order the larger size.




One method that works (for only Arai and SHOEI) for size checking is to use genuine issue boonie hat.
Go to the military surplus store and try them on.

(https://farm2.staticflickr.com/1943/45546400331_52625c9fb1.jpg)

The brand doesn’t matter, as long as it’s made to proper specification which is MIL-H-44105B.

For example, the size 7 is 55.9 cm. If the size 7 feels too tight, but next size which is 7-1/4 (57.8 cm) fits alright, you should get M, instead S.
If 7-1/2 is too tight, you should get XL, not L.

You know, boonie hat does not stretch, so you should be able to tell clearly if it’s too tight.

SHOEI X-14

One last thing I may add.

Why SHOEI X-14 is so great, in terms of adjustability?

Because it offers more range of adjustment for many different types of the head shape.

You may have forgotten, but my head (looking from the back) has two corners at the top
(almost like I have horns on the back of my head.)

Well, the hair is deceiving. It covers the corners, the irregular bumps on the head.

(https://farm8.staticflickr.com/7916/46477761494_20c5cb6fe9_b.jpg) (https://flic.kr/p/2dP5Feq)

(It also (kind of) acts as buffer zone, between your helmet and skull.)

It looks goofy, but this is how the center pad sits on your head.

(https://farm8.staticflickr.com/7842/46477761974_53f3fb3766_b.jpg) (https://flic.kr/p/2dP5FnG)

If you are having hot spot problem and trying to fix it, then, you really need to take off the liner and wear it,
look into the mirror, figure out which part is pressing hard on your head.

This is the most important for my particular head.
See the gap between the top pad and the side pad (where I am pointing)?

(https://farm8.staticflickr.com/7806/47149415502_53f3fb3766_b.jpg) (https://flic.kr/p/2eQr5yW)

This is how mine is set up.

(https://farm8.staticflickr.com/7828/47149418662_8a5ae56d11_b.jpg) (https://flic.kr/p/2eQr6vq)

See the huge gap there? That’s where my horns go through.

(https://farm8.staticflickr.com/7816/46477761934_386ab124b7_b.jpg) (https://flic.kr/p/2dP5Fn1)

Now, if I close that gap there, like this ...
(https://farm8.staticflickr.com/7849/32259059047_3587f87426_b.jpg) (https://flic.kr/p/R9C7ne)

... then, it will give me some very annoying pressure point ...

(https://farm8.staticflickr.com/7863/47149415172_20c5cb6fe9_b.jpg) (https://flic.kr/p/2eQr5tf)

... even though it is exactly the same helmet with the same liner ...

If you ever decide to try X-14, don’t disregard it just because it doesn’t fit exactly right
when you first try at the shop (or purchasing from online store.)

Pull out the center pad (which is very easy) and try closing / enlarging the gap between each pads.

You can also do it on the road side if you want to experiment.




Snap off one side at the back...

(https://farm8.staticflickr.com/7808/47149416202_84813a8d66_b.jpg) (https://flic.kr/p/2eQr5M1)

Snap off the other side ...

(https://farm8.staticflickr.com/7806/47149416722_f28f7366f5_b.jpg) (https://flic.kr/p/2eQr5VY)

Pull the front portion out from the eye port opening ...

(https://farm8.staticflickr.com/7859/47149415822_8876a99900_b.jpg) (https://flic.kr/p/2eQr5Es)

... can you see better?

(https://farm8.staticflickr.com/7845/47149415472_c64a2ef469_b.jpg) (https://flic.kr/p/2eQr5yq)

Then, just pull out the entire center pad

(https://farm8.staticflickr.com/7920/47149417642_668d0d6cd0_b.jpg) (https://flic.kr/p/2eQr6cQ)

No need to mess around with cheek pads or chin strap.
This is one of the best design out there.

Thanks so much for the education bro [thumbsup]. I will keep this in mind when looking for my next helmet, which I know will be an AGV. I have had to add foam to reduce noise in my HJC size L, while Shark and AGV generally fit me in size M and are queit helmets for my cranial morphology. Explains why some helmets with a reputation for quiet operation are noisy and vice versa.
I will refer people to this thread.
Thanks again.

About "replacing helmet after 5 years" thing
So, you have the helmet that you can happily wear for hours without pain, but doesn't slip around on your head.

Do you have to replace it after 5 years, as some people say?

I was kinda hesitant to post this, (because this may "open up the whole can of worms"),  and it's not directly related to hot spot/ fitting problem.
 ,but, in the end, decided to post against my better judgment. (I originaly wrote this for ADV rider’s thread, regarding the helmet’s “sell by date”.)

First of all, I want all of you to understand that this is what SHOEI North Amarica, who is a distributor, NOT the actual helmet manufacturer, says.
(Yes, yes, I understand that for us who live in US and Canada, SHOEI North America IS SHOEI (since SHOEI Helmet in Japan won't directly communicate / do business with us), but still, you have to understand that what they(SHOEI North America) say is NOT exactly the same as
what SHOEI Helmet in Japan (as a manufacturer) says.


Now ,...

Let's get clear about the fact that SHOEI North America NEVER said the helmet is not safe to use after 5 years from the date of manufacture.
What they say, is
Even if none of these is applied, we, SHOEI, recommend replacement in 5 years after it's first purchased at retail.

(exempt from here

Helmet Replacement
Ultimately, the useful service life of a safety helmet is dependent on the intensity and frequency of its use. Helmet replacement is recommended even if only one of the under-mentioned points applies:
1. The helmet was subjected to an impact.
2. The comfort padding or the retention system has become loose due to heavy use or display signs of deterioration. Test: with the retention system fastened, the helmet turns to the side when you gently shake your head.
3. The EPS liner has come away from the helmet shell.
4. The EPS liner shows signs of wear and is beginning to break up, or if it has been exposed to heat or a solvent and has melted. There are indentations in the EPS liner and/or white scratches can be seen on surfaces with black paint.
5. Even if none of these is applied, we, SHOEI, recommend replacement in 5 years after it's first purchased at retail.  )

The "5-year" time frame is NOT based on the research (of how much deterioration happens over the years).
It is decided that way for the sake of convenience (5-year limited time warranty).
(Arai North America, Schuberth North America, they all do the same. 5-year limited time warranty, recommending the helmet replacement after 5 years of use.)

You know what Arai and SHOEI (and OGK) say, in Japanese domestic market?

Let's take a look at the manuals of JDM version.

(https://lh3.googleusercontent.com/GA1kcWNotkbwzAiiJwxEMykOkzIFG2BmGp9Kjojc_Bgnzwl37bmyoypCXkB5J3jgAw8r6M3RKi6GIkKLp8QhqzzLvGy0ZtEzsveAiLqsRij5hHOlxjSQpbtFgGBrkJmFYyw_AafAnA=w2400)


Arai

(https://lh3.googleusercontent.com/PXmh20mFD0WXptoh1IZ-pmVYDR6UjHuWUkzTROb4zojLL1bOFJf85dY-rZ7aUioYReme4hxrVnHZSN92JfsCR5P-QESGqPhx4jLnonxV6QC8m_ss8YZawkzFhKwv_3hQjt4EEIB0WQ=w2400)

(https://lh3.googleusercontent.com/tWJ_Wg0K_xsSzgZBq3ZpL_CIx6wUxINNzgQWLXoHGdKONQRYQIsS5Qc44RNbQ3SolyWiJpVLnMKDIm_aoEtt3b5z1k0uklicnIOPVZFXZ_UK78XtolMyjovwUuycz8aJ3ybZSU-A3w=w2400)



SHOEI

(https://lh3.googleusercontent.com/hYERQElxqASsdfw50Ii_3hcFaxtFP2K6uUKCde-dmkpdbqZCFq0VjfJpssD3x2TnxfOAUNSFDFaPM-k03n9krz7jmtWx8iqpXugdizdfkTrFWKS71sPfNKeQ-FhJ7vNA9SvCCVSeTg=w2400)



Yes, I know you can't read them.
But, you can see "SG" (ＳＧマーク= SG mark = SG sticker) in both Arai and SHOEI's manuals.
You can also see "3" in SHOEI's manual.
(In Arai Manual, it is writeen in Kanji character,  "三" (means 3)).

What they are telling you is that they recommend to replace the helmet
AFTER 3 YEARS from the date of purchase.


Yes, 3 years.

They are telling their customers in Japan to replace their X-14 after 3 years from the date of purchase.

WHY?

Because of these.

(https://lh3.googleusercontent.com/wvvjn15cxROG5dJj1dDdROxLT9tKhHRBRqVF8xS9n2y7JiSVPmgPRjSDCzq4vpAEkwRDF4G08enxGKPRm_BmPPTGQdEcEoMf9V3_hsa2HlP0xtu59ZEsYWl9hOxWDuFAaCqzzstIHA=w2400)

Close Up

(https://lh3.googleusercontent.com/vIg7nHChXJziquiSYdLwgQhK7D3XAnH20f4r9J84z5QWdSqvgLP6MexDHmQknLwqq9e8BRkH_y5NbX_-p5V_zE6Bqm0bdkjOt66jJXPMl6PON_PJ6F53_wEv5uumUYhGw1UXLUbQow=w2400)


(https://lh3.googleusercontent.com/bAp0s4yY1xWapeqdZG-w66l3MqLwpSWGDjzD-SBwWO3STlMIVwHuYGzmgfr-dLxIkj-eQYbzoHrusbF3rGz5m6emsYh3wGqa5xbwGQs7R15qpaT_bEUp_tBW9_yNurn0H34V7hus5A=w2400)

(https://lh3.googleusercontent.com/-XQkwixD5BYq8-0hukXuDBebsow6eBJ4YX9cGl2TWGFsH4Ui_gudOI5P4MVKpsVB3R_zJ6Z1lkphQPAfYIQOTlLW-f8zc1Azp-v4bVncx1evjTrS7K7VvoMREjTENlmGVFQAexUkmA=w2400)





Can you see this ?

(https://www.d-storefukuoka.com/wp-content/uploads/2014/03/cp_05.gif)

This is the sort of "insurance" system they have in Japan that expires after 3 years from the date of purchase.

These things have "SG sticker" ...

(https://item-shopping.c.yimg.jp/i/l/montaukonline_n-bhl270-1100-jo)

These things (folding walking cane) have SG sticker ...

(https://item-shopping.c.yimg.jp/i/j/zakkashop-kaguyahime_ismk10492)

They (the manufacturers of motorcycle helmet, boys baseball helmet, walking canes ) have to pay fairly huge amount of money and get their products certified. Otherwise, the products cannot be sold as "motorcycle helmets" or "baseball helmets" or "walking cane".
(Without certification and SG sticker, these things can be sold only as "for decoration", it's illegal to sell them as motorcycle helmet / baseball helmet / cane / cooking pot / whatever ....)

So, they tell their customers (in Japan) that they recommend to replace the helmet after 3 years, based on this system.
Not because the helmet gets deteriorated and becomes unsafe after 3 years.


As far as I could remember, this (3-year time frame for recommending helmet replacement) has not changed from all the way back to the early 1980s (when I started wearing motorcycle helmet).

So, the helmet manufacturers NEVER said the helmet is unsafe to use after 5 years from the date of manufacture.
The distributors (SHOEI North America, Arai North America, Schuberth North America, etc etc) NEVER said that either.

Very interesting and useful information. Thanks again. [thumbsup] [beer]

Your welcome.
Glad that you find the information useful.
(The info I shared here, will (most probably) never come out from the online helmet seller, distributor, etc.
That's why, for example, Revzilla (& other online retailer ) are making same old "how to choose helmet" video over and over again. )

Just a heads-up.

You can no longer buy Arai and SHOEI helmets from oversea vendors.
(They may still sell other brands, buy won't sell Arai and SHOEI (and their genuine accessories / parts) to US customers.)

More details in here.

http://www.ducatimonsterforum.org/index.php?topic=78308.0

https://youtu.be/Yv1ACzEfWUw

So, you need sculptor’s caliper, to measure your head’s front to back,
side to side.

Here’s how to make one, with (almost) ZERO budget.

Ingredients

Cardboard box from B&H
(Any cardboard box will do.)


Gaffa tape
(Duct tape can be used. But Gaffa tape is better.)


Bamboo chop sticks


Cloth clip


Tools
Leatherman MUT
(To cut down bamboo chop stick)


Hinderer investigator pen
(Any sharp, pointy object  will do)


Now,

You can measure your head,

And  helmet internal.