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I’ve fallen a couple times, but no serious damage is visible on the helmet except for a couple divots here and there.

Should I consistently be replacing my helmet after a certain amount of time? After every relatively serious fall?

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Climbing... with a bicycle helmet? –  Henrik Hansen May 4 '12 at 11:41
    
See also bicycles.stackexchange.com/questions/5836/… –  naught101 May 11 '12 at 8:59

8 Answers 8

up vote 40 down vote accepted

Helmets should be replaced roughly every 5 years and after any crash where your head makes contact with the ground.

Helmets will crumble, compress or otherwise deform in sometimes hard to see ways when you hit the deck. The structural integrity of the thing will be massively diminished after even a relatively tame fall. This is one area where you don't want to mess around much.

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+1 for "after any crash where your head makes contact with the ground". Modern helmets are not multi-use .. there lifetime is one impact. –  tomjedrz Sep 2 '10 at 18:45
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What about a crash where your head makes contact with, not the ground, but, say, a car or a telephone pole? –  Neil Fein Sep 2 '10 at 23:06
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@neilfein - check your helmet's warranty and manual to see exactly what kind of solid objects it recommends crashing into. ;-) –  matt smillie Sep 2 '10 at 23:22
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The safe thing to do is to replace it after any crash, regardless of whether you hit the ground, a telephone pole, or a car. –  nhinkle Sep 2 '10 at 23:39
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If it's saved your noggin at least once, it deserves its retirement! –  darkcanuck Sep 3 '10 at 1:16

Why are you using a helmet?

If you're using it because you're doing something which involves a decent probability of you falling and hitting your head, then you should probably replace it after every serious incident. Some companies (e.g. Giro) will give you a discount if you trade in a damaged lid, so that they can learn from its demise.

If you're commuting or doing something less dangerous, but which offers some scenarios where you think a lid will assist, then you might be less concerned about replacing after every ding. But the helmet is designed to work when pristene; as soon as there is damage, any damage, it won't act in the way that is was designed to, so is going to offer you a sub-optimal service.

But if you're just using a helmet because you think you should, although remain generally unconvinced (peer pressure, race rules, certain state/national legal obligations, enhanced air flow around the scalp), then don't worry about it ...

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What about if you're using the helmet to have a place to mount your mirror? –  Daniel R Hicks Sep 6 '11 at 17:55
    
If one was to be unkind, one might speculate on how much inside the head is worth protecting if you're using a helmet mounted mirror. But I'm not an unkind type of person ;) –  Unsliced Sep 6 '11 at 20:40
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If I'd ever found a different sort of mirror that worked I'd use it. –  Daniel R Hicks Sep 6 '11 at 21:50
    
+1 for the comprehensive coverage of viewpoints –  naught101 May 11 '12 at 9:02

It depends what you use it for. The primary advantage I have from my helmet is not hitting the branches with my head, when riding in forest. For that I don't need a new one each 2 years. I even heard that this is actually what bike helmets were made for in the first place.

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If you use it everyday in sunlight you might find that the plastic is beginning to crack after 2 years. And for me the straps and lining are getting pretty disgusting –  mgb Mar 4 '11 at 3:14

When to replace a bicycle helmet:

  1. Any fall that impacted the helmet. There can easily be hard to see cracks, crumbling or compression of the foam; and all of those will make the helmet less effective.
  2. If you dropped it pretty hard and there's any likelihood of damage.
  3. If the outer shell is separating from the foam. The shell helps protect your neck. Also, if the shell is separating it may indicate the foam has compressed.
  4. If the outer shell has any significant scuffing. One of the ways that a helmet protects you is by helping your head to slide across rough surfaces instead of sticking, so if the helmet surface is now rough instead of smooth you lose that protection.
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The general rule is every 3-4 years or after a crash. Some people say that excessive sweat or UV exposure can also degrade your helmet, but no one has proven that so far.

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On one hand we are always being told that plastics take thousands of years to degrade; on the other, apparently a plastic helmet is useless after 4 years. I can't believe both of these statements are true! –  Jonny Cundall Sep 17 '10 at 8:35
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"Degrade" does not mean the same thing as "Decompose". Most man made materials take decades to decompose (break down into their component elements), but only a few months or years to degrade (become significantly weaker or structurally deficient). –  Gary.Ray Oct 11 '10 at 3:22

Bicycle helmets are designed to absorb impact by cracking or crumbling. The insides of the helmet may crack with no damage visible on the outside. I'd replace the helmet as soon as you can.

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Well, by becoming compressed. I cracked piece of polystyrene is a piece of polystyrene that is not distributing energy. –  Tom Hawtin - tackline Sep 4 '10 at 14:52

Inspect the helmet for damage inside and out. If you see any cracks, then it's time to replace it. If not, you're fine. You don't want to risk your cranium when you could just buy another helmet.

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What about cracks you can't see? –  naught101 May 11 '12 at 9:04
    
You should replace it if there are any of those, too. –  Michael Jun 10 '13 at 22:57

If there's visible damage to your helmet, like a crack, then you should definitely replace it. Dents, maybe, it depends how bad they are. Better safe than sorry right?

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