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Helmet Replacement, what are the general guidelines?

desmojendesmojen Posts: 136
edited July 2010 in MTB general
Hi all,

I had an off last night during which I hit my head pretty hard. I had on my helmet luckily enough and don't seem to have damaged myself beyond a bit of a headache today.
My helmet bears no real scars, a few scratches and marks is all, but I did hit it very hard.

Is it the general view that it should now be replaced, as it is in the motorcycle world?

Jen.

Posts

  • desmojendesmojen Posts: 136
    Thanks Cat. I thought as much but wanted to check.

    New helmet now ordered, hopefully to arrive before my next ride :)

    Jen.
  • BigShotBigShot Posts: 151
    If you basically nutted the floor then yea, just replace the helmet and take it easy.
    If there was much rotation of your head when you hit, get along to a hospital at the first sign of the headache (or anything associated, like nausea) as you can get some pretty nasty injuries from rotational stuff.

    Me? I'd probably get a few ice-packs/bags of peas in the freezer and keep the noggin cool until I knew all was well.

    Out of interest, what can you see on the lid with regards to scrapes, compressed or cracked foam and so on?
  • desmojendesmojen Posts: 136
    There is very little to suggest it has been hit at all. Some very light scratches, a paint mark from the visor and the little strap holder thingy was knocked slightly out of its slot and that is about it. There is no visible sign of squashed foam, no cracking and no delamination to suggest internal movement of the polystyrene (although I know it will be there).

    Luckily enough I guess, the floor I hit was relatively soft and I managed to miss all the trees. I say lucky because I had nothing to do with it, I fell so quickly that I didn't even have time to stick my arm out, hence landing on my swede!

    No rotation or anything like that. I've had a headache since a few minutes after I fell, and I'm a little bit dazed and confused feeling. Nothing a couple of easy days won't sort out :)

    Jen.
  • BigShotBigShot Posts: 151
    Interesting that. If it was me I'd be inclined to take a saw or a hotwire to the lid once I'd got the new one. I couldn't rest without getting my calipers on it to find out if it had actually done anything.

    I ask cos I find the whole helmet thing kinda fascinating. I always wear one off road but almost never on road for a whole host of reasons. If the foam didn't deform the chances are the helmet did very little to reduce the impact. I've seen it sorta-convincingly argued that the foam in bike lids might actually be too hard.

    My inner nerd wouldn't be able to resist investigating further. :P

    As for a couple of easy days...
    ...I dunno, you must be pretty groggy... better take a week to be on the safe side. ;)
  • cat_with_no_tailcat_with_no_tail Posts: 12,981
    Helmets are not designed to be re-usable. If you've nobbled your bonce hard enough that it's given you a headache, it needs to be replaced. When it comes to noodle safety, best to take no chances.
    In a crash, I can see a damaged helmet actually being more dangerous than no helmet at all.

    Also, it's still worth a trip to A&E imho. Head injuries get priority so you shouldn't have to wait too long to be seen. Chances are that it's nothing a good nights sleep and a couple of asprin wont cure, but best to get it looked at anyway.
  • desmojendesmojen Posts: 136
    BigShot wrote:
    Interesting that. If it was me I'd be inclined to take a saw or a hotwire to the lid once I'd got the new one. I couldn't rest without getting my calipers on it to find out if it had actually done anything.

    I ask cos I find the whole helmet thing kinda fascinating. I always wear one off road but almost never on road for a whole host of reasons. If the foam didn't deform the chances are the helmet did very little to reduce the impact. I've seen it sorta-convincingly argued that the foam in bike lids might actually be too hard.

    My inner nerd wouldn't be able to resist investigating further. :P

    As for a couple of easy days...
    ...I dunno, you must be pretty groggy... better take a week to be on the safe side. ;)

    Thats a good point actually, the foam is pretty tough stuff. I would guess that it has to be due to the outer shell not being very strong (relative to a motorcycle helmet for instance).
    I think though, that even if the foam didn't deform very much in my specific case, the lid would have spread the impact somewhat more than my head would have done without it.
    I also think that the foam would come into play much more if you hit something a bit less soft, like a tree or a rock.

    Either way, I agree with Cat, it isn't clever taking chances with this kind of thing. I guess I was just a bit peeved at having to spend out to replace it. I will keep all the receipts etc this time and make use of crash replacement offers next time!

    Jen.
  • BigShotBigShot Posts: 151
    Crash replacement offers are great. It still seems like a racket when you're the kind of rider who likes the "if you didn't crash you weren't trying hard enough" approach but a LOT better than paying full retail price for them.

    I believe the shell of a helmet is there mainly because it's more likely to slide than bare foam would. It's still not slidy *enough* to prevent the rotational injuries (see Phillips Head Protection System for the logic and solution behind that) but better than it would be. Motorcycle helmets mainly offer more protection due to the massive increase in foam over bicycle helmets. That's impractical for cyclists as the increased weight and size would affect balance and the enclosed nature would be problematic for overheating while exercising.

    To complicate things a bit - cycle helmets are designed to mitigate linear impact forces (which cause relatively benign injuries like cuts, bruises and concussions) and they serve that purpose to some degree. The scary part is that they can actually turn linear forces into rotational forces with potentially disabling or lethal consequences (coming from diffuse axonal injury and subdural haematoma). Fun eh?

    That last part is one of the big reasons I don't wear a helmet on the road... the seemingly (backed up only by the way it looks to me, not by any stats or science) rare incidence of serious brain injury in off-road riding leads me to think something else is at play there. It may be an expectation of falling, lower speed or something else - but I feel right enough wearing a lid off road (and always do) - but on road I don't like it.

    Quite right that it's daft to take chances with your head. When relying on a helmet it needs to be used within design paramaters to do the job it's designed for. Since they are designed for single impact use they really do need replacing after a knock.
    Of course - single impact is not the same as single crash. The best approach is to do all you can to keep your head from hitting the ground/tree/rock/wall and relying on the helmet only when you fail to manage that.

    Kinda ride like you're bare-headed even though you know you're not.

    So - which shiny new lid are you getting? I'm going to need to get one myself now I'm getting back into off-road riding, my old one doesn't fit any more.
  • desmojendesmojen Posts: 136
    I am replacing like with like - Giro Athlon. My last one is a couple of years old hence the lack of receipts etc. Found a new one on e bay for £70 so I went with that.

    You seem clued up on helmetage, are there any protection standards in play like there are for motorbike ones?

    Jen.
  • I've needed a helmet ever since I checked it at Llandegla :lol:
  • BigShotBigShot Posts: 151
    TNM
    Sounds like there's a good story behind that.
    One of my best was a good hard crash into a drystone wall. The helmet stopped by brain-box hitting the wall but the left side of my jaw got a clattering (as did my left shoulder, forearm, elbow and thigh... followed by my right side being clattered by the bike as it followed me in). Still got that helmet - couldn't even afford to replace it under crash replacement!


    Desmojen
    There's a site absolutely jam packed with analasys of the science, stats, legislation and so on surrounding cycle helmets at cyclehelmets.org
    Starting with the "Cycle Helmets Overview" link at the top will give their general take on it all and as you read through bits you'll come across links to more detailed explanations of what's going on.

    It's aimed more at road cycling and goes into things like the effects of helmets on driver behaviour, risk compensation (acting in a riskier way if you feel protected by something), the effects of helmet laws on safety, how the standards are arrived at, the anatomy of head injuries and more. It's a pretty well organised site though so it's not too hard to filter out the noise.
    It's worth bearing in mind that though it's based on road lids, the same standards and physics apply to the ones we use off-road.

    Yes, there are standards at play. Have a look at the "Heads Up - the science of cycle helmets" link (it's a PDF) on the overview page for more detail but in short, helmets are tested on a variety of anvils using weighted headforms and the forces measured.

    In the early 1990s a British Standard applied but now there's a lesser EU standard that applies and has actually lowered the bar. All UK bike shops sell helmets that conform to EN*somethingorother* (4 digit number, can't remember it) - or at least, they should. That's the required minimum standard.

    You've just to to remember that they are designed for a single impact, with straight-line forces, at low speed and on a flat surface. Third parties (cars) and uneven hard surfaces (kerbs, rocks, trees, railings and so on) change the dynamics and reduce the effectiveness of the helmet. If you're aware they are designed to prevent cuts, bruises and (maybe) concussions you're thinking along the right lines. If you're expecting protection from serious head injury they aren't so hot.
  • ChrisSAChrisSA Posts: 455
    Useful topic.

    I find myself asking the replacement question, sitting here with my arm in a sling. Headache went the same night of my off-road prang.
  • cat_with_no_tailcat_with_no_tail Posts: 12,981
    I've needed a helmet ever since I checked it at Llandegla :lol:

    Hahaha, wasn't that when we were there? And you've still not got one?

    Still, I bet it encourages you not to fall off :lol:
  • stumpyjonstumpyjon Posts: 4,069
    On a different note it's now recommended that you replace your helmet every three years regardless of whether it's been in a crash.
    It's easier to ask for forgiveness than for permission.

    I've bought a new bike....ouch - result
    Can I buy a new bike?...No - no result
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