https://www.helmet.beam.vt.edu/bicycle-helmet-ratings.html#!
So no test is perfect, we all know that, and some folk will take issue with some of VA Tech’s work, but it’s reasonably well respected stuff I think - which leads me to my question.
Most of us regard full face helmets as more protective not less, but they don’t do well on the VA Tech studies.
Actually some do plain badly (221st of 277 cycling helmets of all types tested), and the best two are 9th and 40th respectively.
Why?
Is it the chin piece creating a rotational problem perhaps?
I note that motorcycle helmets generally don’t have such a pronounced chin - at least on road.
Thoughts?
Is it the same protocol for both trail and full face helmet?
No looked for a while but I thought they were two different tests.
Then the scores are converted into a quick star rating. Might this explain the difference?
Nothing to suggest the tests are different - at least if there is I missed it.
Perhaps what does and doesn't count, and how they're weighted, is making the difference.
For example, if there's no credit given for saving a broken jaw. Or there is, but doesn't make up for a higher likelihood of a twisted neck.
It could be argued that the ideal weighting depends on the type of use.
The method is published here.
In summary the head is dropped onto a kerb in different orientations and the resultant acceleration (in 3 dimensions and rotational) is measured.
There is no testing of the chin, it's all done with impacts to the top of the head.
The impacts are based on 50th and90th percentile recorded date for impacts, I assume that's the 10% most severe. Bearing in mind the test is carried out multiple times one one helmet, and in the real word when people crash the helmet is frequently cracked or otherwise completely destroyed.
The STAR system weights the results against real world recorded impacts to produce a score that signifies the likelihood of a concussion if you were subject to those impacts. So it assumes you're going to crash on your head repeatedly (it's derived from a similar test for American Football helmets). So the end result is I think a bit like a pass/fail for different average transmitted force levels for each star rating?
Whereas the perceived extra safety of a FF is
a) to your face
b) that it will protect against a single much larger impact, i.e the 99th percentile or worse, not the 90th.
I suspect if you devised a different test where a fresh helmets were dropped with progressively higher energy you'd see trail/road helmets doing well initially until they stopped offering any further protection whereas hard-shell FF helmets with relatively solid PS liners would probably carry on offering protection long after the lighter helmets literally crumbled.
