(Peter Rosenfed) wrote in message om...


As a helmet agnostic, I'll have to chime in. People always say there
helmet "cracked" and so must have saved them. This really annoys me.

Helmets do not protect your head by "cracking". They crack because the
foam used is brittle, but the foam absorbs almost no energy when it
cracks. The foam absorbs energy by compressing. If all that happened
is that the helmet "cracked" with little or no compression, then it
did not, in this case, help protect your head. If, on closer
examination, you see that the foam is partially flattened out
somewhere, then the helmet did its job and absorbed significant
energy.

Modern shells hide most or all of the compression in the foam under them,
so most folks look at a helmet after an accident, see a crack, and figure
that is the extent of the damage. If they peeled off the plastic shell
they will usually find a lot more underneath. It will be unusual for
one to see the flattened or dented foam without doing a bit of dismantling,
which is not as easy with the newer fusion styles as it was with the older
non-fusion styles.

I have had 4 accidents in the last 20 years where I landed partially or
fully on the head. All 4 helmets involved in those accidents suffered
significant compression of the foam. The worst that happened to me, as
far as head injury, was getting knocked unconscious for an hour or so;
they listed a concussion on that due to the loss of consciousness, but
there was other symptoms of the concussion or head injury (even ran a
CT scan). In the first of the 4 accidents I was vaulted up and over
traffic, and landed head first. Again, no head injury but the foam was
compressed significantly. In only one of the 4 cases did the helmet
crack, and that was following a line between two air vents.

In the end, the best course of action after hitting one's helmeted head
is to replace the helmet even if there is no sign of damage. Bell/Giro
has a good replacement policy. Or one can buy a new one. But personally
I would not use one that has hit the ground.

- rick warner