How to solve helmet hot spot problem

Discussion in 'Equipment' started by S21FOLGORE, Sep 7, 2018.

  1. S21FOLGORE

    S21FOLGORE Been here awhile

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    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
    [​IMG][/url]Hot spot 18, 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 for male and female.

    What matters for 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.
    #21
  2. S21FOLGORE

    S21FOLGORE Been here awhile

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    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 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 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 types) 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 your head will not help.
    You only get reply that says to look at the manufacturer’s sizing chart.



    ... to be continued...
    #22
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  3. GS2Trout

    GS2Trout Adventurer Supporter

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    S21, thanks for that info! By any chance, did you run across any modular helmets that might fit?
    #23
  4. Chaostrophy

    Chaostrophy Been here awhile

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    I'm bummed, then again, I'm super happy with the fit of my Arai Signet X.

    Sent from my Nexus 6P using Tapatalk
    #24
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  5. FMFDOC

    FMFDOC IBA #63181 Super Supporter

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    I may have already tried one of those. If I can find one in my size I'll try it again.
    #25
  6. Gone Troppo

    Gone Troppo Somewhat bemused observer Supporter

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    Brilliant thread - thanks.
    #26
  7. Hammerdown77

    Hammerdown77 Long timer

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    CI for the AGV AX-8 Evo is 94? That's surprising, since the online reviews (Revzilla, for instance) call that helmet "Intermediate Oval".

    Seems like it's really round for that number. Do they then use padding in it to make it IO? I was considering trying one, but not if it's that round.

    EDIT: Whoops, look like you explained that in the post further up. I might try that one anyway, as I do have kind of an egg shaped head, just with a slightly wider forehead.
    #27
  8. S21FOLGORE

    S21FOLGORE Been here awhile

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    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)
    [​IMG]


    From left to right, C3 Pro, RX-7-X, GP Tech

    [​IMG]


    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?

    [​IMG]

    [​IMG]

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

    Incidentally, the same story applies to GP tech.

    [​IMG]

    [​IMG]

    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.
    [​IMG]

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


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

    [​IMG]

    You (somewhat) feel the EPSl 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.
    On the surface, With CI=75 head, you have opposite problem from mine , but essentially they are the same problem at the root.
    Yes, the helmet manufacturers and the shop (authorized helmet dealers) really need to do more.
    #28
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  9. S/W

    S/W Long timer

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    I asked BELL a couple of months ago, and was told they are still doing the "CUSTOM FIT". The cost was close to a grand. Expensive yes, but, I couldn't find a helmet that fit me (even bought an ARAI, which didn't fit) . I threw away four helmets (if i remember right) when I got my Custom Fit. It fit perfectly!! and is Snell Approved. If you can find a helmet that fits for cheaper money, buy it. If you can't, it doesn't matter what shape your head is, round, long,triangular, whatever, Bell will scan your head and make a helmet for you that fits your head perfectly!! It's the most expensive and the cheapest helmet I could find that fit.
    Check the BELL website to find out where they are scanning, some of their sales reps have the scanner and will meet you at a dealer.
    #29
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  10. Gone Troppo

    Gone Troppo Somewhat bemused observer Supporter

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    I have a custom racing suit....a helmet would be wonderful...
    #30
  11. Gone Troppo

    Gone Troppo Somewhat bemused observer Supporter

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    I have a round head, probably CI of 85+

    I have a quantum x, which fits well. Also have two Shoei RF1200/NXR, which fit OK, although slightly narrow in the sides. I used wider cheek pads.

    I do find the Shoei head liner softer than the Arai.

    Interested in your comments on the Shoei x14/spirit 3 being good for high CI...I tried one on, and it wasn’t bad...
    #31
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  12. Hammerdown77

    Hammerdown77 Long timer

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    Do you get pressure on your ear cartilage at all with the RF1200? That's the only complaint I have with mine. I had none of that with the Qwest
    #32
  13. Gone Troppo

    Gone Troppo Somewhat bemused observer Supporter

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    Yes! Exactly! :thumb

    It is OK without earplugs, but can be annoying with them in - especially as my plugs are not completely flush with the ears.

    I also owned a QWEST previously - it was great, but heavy...
    #33
  14. Hammerdown77

    Hammerdown77 Long timer

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    YES! Exactly the same with me.
    Man, you're like a brother from another mother...
    #34
  15. Gone Troppo

    Gone Troppo Somewhat bemused observer Supporter

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    :lol3
    #35
  16. floalex

    floalex Been here awhile

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    I have an CI of 75 (15cm wide / 20cm long). In almost every helmet I either have the problem that my nose is almost touching the visor or that I have pressure on the top of my front head.

    I’ll get an Nexx X.Wed2 in Size M next week. The shop which ordered it for me will adjust (add?) the lining in the front top area. By putting more cushion the weight should move to the back and relieve the pain.

    Maybe later I have to add thicker cheek pads.
    #36
  17. S/W

    S/W Long timer

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    Unfortunately, I received an Email from Bell customer service today, which stated they have stopped the "Custom Fit" helmet program. Sad news for us who have hard to fit heads. Maybe another company will develop a product that works as well as the "Custom Fit" helmet did for me. Maybe they don't realize what a public service providing helmets that fit properly was for the riding public.
    #37
  18. Gone Troppo

    Gone Troppo Somewhat bemused observer Supporter

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    That's a shame!
    #38
  19. S21FOLGORE

    S21FOLGORE Been here awhile

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    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 applies to all type of head / helmet internal shape.)

    Example story

    [​IMG]

    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 ...

    [​IMG]

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

    [​IMG]

    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

    [​IMG]


    RT-33 2-shell size

    [​IMG]



    First, let’s take a look at X-14.
    They come in 4 different shell sizes, 5 different EPS liner.
    S(S and XS use the same shell), M, L, and XL (XL and XXL use the same shell).

    fig.19

    [​IMG]


    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

    [​IMG]


    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, and that will tolerate the slightly oversized head (56.5 cm) without problem, even if your head has 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 with 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.

    [​IMG]

    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 of 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.
    #39
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  20. Gone Troppo

    Gone Troppo Somewhat bemused observer Supporter

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    Excellent info. Thanks again.
    #40