Virginia tech 5 star vs ASTM DH helmet ratings...FIGHT!

Bump/tick as I'd be interested in the outcome of this.
I always used to buy Snell helmets and stick with Giro since then. Never even noticed that Snell was no longer a thing.

Slower speed and more angles sounds like it would suit my riding better but I'm not DH rider. Trail helmets for me.

I don't think I've ever considered either. I just buy the giro that fits my budget.

The interesting thing looking at the Virginia Tech site and some of their methodology is that while they claim to assess for both linear impact and rotational injuries many of their tests still just use a dropped Noggin proxy, surely if rotational injury is being properly assessed the loads it imposes on the spine/trunk of a more complete ergonome/dummy and/or more representative accident conditions (discuss)?

They seem to do more permutations on oblique angle testing with a variety of set angles and rotations mostly against a 45deg anvil and I assume they've measuring each of these with a 6DOF accelerometer of some sort(?) it's not stated.

It's good that the assessments are sport/activity specific, but their 5 Star rating is still just a weighted and averaged scheme to give a single simple "score". So potential users might still want to delve into the details of testing and understand performance against specific test cases (if that data is available), I also couldn't see (on a cursory skim TBF) specifically what testing they do differently for DH helmets Vs others... Noting:

Each lab impact is weighted based on how often a cyclist might experience a similar impact. We compute concussion risk from measured peak linear acceleration and rotational velocity for each test. Each risk is multiplied by its weighting factor and then summed together to compute an overall score. The overall score estimates the number of concussions the average person would see if they experienced identical impacts at rates matching their weightings while cycling.

A lower score indicates better helmet performance.

So do they just run the same 24 impact tests and then tweak those weighted probabilities based on probable injuries for DH as an application vs say Trail riding Vs Road? or do they run a different set of tests for each sport/activity? It's still what I'd call a bit fuzzy.

It's a methodical approach to testing something, which is a good thing, these things are always going to be flawed in some way, nothing is perfect.
But I still can't see how punters are supposed to make beneficial use of it, other than balancing a number of 'stars' (that they don't fully understand the testing behind) against the asking price of a lid...

You still just take their star score on trust from what I can tell.

But I still can’t see how punters are supposed to make beneficial use of it, other than balancing a number of ‘stars’ (that they don’t fully understand the testing behind) against the asking price of a lid…

Exactly this, more stars better than fewer stars...and trust that they have a sound method of awarding stars

But a helmet such as the Fox Dropframe Pro was given the highest rating at the time by Virginia tech (link to fox's marketing) - but it doesnt have ASTM downhill rating...so is ASTM tougher to achieve or just that Fox didnt feel the need to submit their lid to ASTM tests?

The Dropframe doesn't have a chin bar. It was my understanding that the ASTM DH test includes impacts on the chin bar, therefore the Dropframe can't be tested to the ASTM DH spec.

<hr />

so there is some info available on the 2 sets of tests but a side by side comparison isnt easy

ASTM f1952 - ASTM's Downhill Mountain Bike Racing helmet standard

Virginia tech Star rating test protocol - http://hdl.handle.net/10919/83760   which is a link on this virginia tech page Bicycle Helmet Ratings (vt.edu)

VT might have some higher velocities and different angles, ASTM uses different shaped anvils...and chinbars arent necessary for ASTM

links are above in case anyone wants to take a trip down this rabbit hole and report back... 🙂

I stand corrected. Are many or any manufacturers testing their open face helmets to the DH standard? Maybe it's just a design intent thing. Note that F1952 helmets are heavier than road helmets and their harder foam to meet the more severe impact requirements may affect performance in lower level impacts

There is also a Dutch speed pedelec helmet standard to muddy the waters further. https://www.serfas.com/nta-8776-e-bike-helmet-certification-and-why-its-important/

Finkill
Full Member

The Dropframe doesn’t have a chin bar. It was my understanding that the ASTM DH test includes impacts on the chin bar, therefore the Dropframe can’t be tested to the ASTM DH spec.

It's one of the big fudges of F1952, if you have a chinbar it gets tested, if you don't it doesn't. So you can have an open face helmet that gains the standard, but the exact same helmet with a protective-but-1%-beaneath-astm-standard chinbar could not gain the standard despite being more protective. As far as I can tell the only reason they did that was to widen the acceptance of the test, because exactly wtf is the point in a DH standard for open faces otherwise?

Overall it felt like a compromised effort- it's better than CPSC but not massively so, and frankly CPSC is a piss weak standard, much like the basic E standard for bike helmets it's a really low bar. It never felt to me like someone really sat down and designed a true dh standard based on medical progress, data gathered etc, they just went "what if CPSC but more". Which is OK! It's still better.

I'm not sure how ASTM DH is doing overall these days, there was definitely a spell where manufacture acceptance/adoption was falling.