I bought a new Giro Savant helmet online and, after unboxing, noticed that the EPS foam seemed to be quite jagged and uneven at the intersection with the dial system (see photos below).

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This does not look like damage to me and the foam was probably cut that way. I have seen a few images/unboxing videos online that also seem to have quite jagged foam at the intersection, so this suggests that maybe most of the Savant helmets are like this.

I am not bothered with the cutting of the foam if it is just cosmetic but obviously I would need to know that the helmet is not compromised before I can use it.

I would really appreciate any advice so that I can determine whether the helmet is safe to use.

  • It's not a problem. Jun 24, 2020 at 16:31
  • @DanielRHicks So it's just cosmetic then? Jun 24, 2020 at 16:37
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    Many helmets are just like that, It's cosmetic. I guess it's just due to the manufacturing process. As I understand some polymer is injected into a mold and then it expands (a liquid turns into foam then solidifies). Some crevises of the mold are not fully filled giving that aspect to the final product. This may be actually by design (i.e. some cavities in the mold are there on purpose to allow the foam to actually get to where it's needed. It may also be where parts of the mold meet and does not make full contact right to the edge, allowing some foam to seep out.
    – Jahaziel
    Jun 24, 2020 at 17:01
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    Understand that the foam adds little structural strength -- the polycarbonate shell is what holds it all together. So long as large chunks of foam are not coming loose the structural integrity and shock-absorbing characteristics of the helmet are not impacted. Jun 24, 2020 at 17:25
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    @Criggie I have already contacted Giro (before even asking the question on SE). I am still awaiting a response, but I will post an answer if/when I do receive a response. Jun 26, 2020 at 16:21

2 Answers 2


The jagged and uneven edges you are seeing around the straps are merely cosmetic. At best they are at the minimum tolerance for manufacturing quality and at worst are an isolated case of tolerances going wrong during production.

Either way, as long as the integrity of the foam in the helmet is not compromised (by virtue of crashing or the like), then it is safe to use. Happy riding!


I am not bothered with the cutting of the foam if it is just cosmetic but obviously I would need to know that the helmet is not compromised before I can use it.

Every single helmet built barely to spec is compromised.

If you consider the bicycle as a rod whose weight is evenly distributed, when the bicycle falls with tire contact point as the pivot point, the moment of inertia is

I = 1/3 * m * L^2

The rotational energy is

E = 1/2 * I * w^2 = 1/2 * I * v^2 / L^2 = 1/6 * m * v^2

When the bicycle falls, its energy comes from its center of mass at approximately height of L/2 converting its potential energy to rotational kinetic energy:

1/6 * m * v^2 = m * g * L/2

Calculating for v:

v^2 = 3 * g * L

Helmet spec (EN 1078) uses v = 5.5 m/s (about) so v^2 = 30.25 m^2/s^2.

In reality, when you fall, you get v^2 = 3 * 9.81 m / s^2 * 1.8 m for a rider with 1.8 meter height. So, in reality, v^2 = 53 m^2/s^2.

So, the speed squared of the head when falling is 75% greater than the speed squared in EN 1078 test. Energy is proportional to speed squared, so its kinetic energy is 75% greater too. For a rider with greater height than 1.8 meters, the problem of underspecced helmets is even more severe.

I wouldn't trust my life to a funny looking expanded polystyrene hat.

I think you'll find every bicycle component and accessory, helmet or otherwise, is built to be as lightweight as possible. The bicycle itself and its components are built to fail in an amount of time most riders consider acceptable. The helmet is constructed to barely pass the helmet tests, which severely underestimate the velocity of the head.

  • 1
    It is still better than an unprotected head.
    – Carel
    Jun 24, 2020 at 19:21
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    My giro helmet saved me 3 weeks ago. I guess it's ok if you dont want to wear one - that's your head. But I cant stand when people like you are telling other not to wear the helmet - will you (or one you) take the responsibility for someones injury? I guess no.
    – k102
    Jun 25, 2020 at 15:01
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    While your figures may be correct (I didn't check your math) I believe your assumptions are invalid. To treat a human being on a bicycle as a rigid rod on top of another rigid rod fails to account for the dynamic nature of a human being during the fall.
    – jwh20
    Jun 25, 2020 at 15:41
  • This doesn't really address the original question at all sorry. And the votes suggest that there's a general disagreement with the points raised here. This is not a question on the effectiveness of helmets, nor the lifespan.
    – Criggie
    Jun 25, 2020 at 22:06
  • @jwh20 I am sorry reality has to follow my simplistic assumptions, otherwise I will not be able to do the maths!
    – Rider_X
    Nov 15, 2020 at 18:34

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