To work as intended, a cycle helmet must fit properly and be replaced when necessary. Here’s what to consider before buying another.

Cycle helmets are designed to reduce the impact of a blow to the head caused by falling from a bike. They’re not designed to start social media flame wars. Yet they do. So before we start, please virtually hug the cyclist to your left, whether they wear a helmet all of the time, some of the time, or never. 

In the UK, these are all legally valid choices. Road traffic law doesn’t require cycle helmets, although competitive cycling events usually do. The Highway Code (Rule 59) says: “you should wear a cycle helmet”. This is a recommendation. If it were law, it would say MUST in capital letters. Assuming you do wear a helmet, however, here’s what you need to know.

When to replace a helmet

According to helmet testing experts the Snell Foundation, a cycle helmet should be replaced after five years even if it has no visible damage. Wear and tear, sweat, chemicals in hair products, and environmental factors all cause gradual degradation – ultimately to the point where an impact won’t be absorbed effectively. Five years is a good guesstimate for a helmet’s lifespan. Some manufacturers recommend replacement after three.

Take good care of your helmet so that it can provide adequate protection until you’re ready to replace it. Store it where it won’t be knocked or squashed. Don’t chuck it in a bag or car boot where it can rattle around. Keep it clean: wash it by hand in cool water with mild soap. Removable pads can go in the washing machine (put them in a mesh bag or similar so you don’t lose them.

If you bang your head while wearing a helmet, the helmet should be replaced. Even without visible denting or cracking, the helmet’s shock absorbing expanded polystyrene may have hairline fractures or compression damage. Many manufacturers offer a crash replacement policy, enabling you to replace your helmet for free or at reduced cost if it suffers crash damage within the first year or two of ownership. This is well worth having for expensive helmets and is convenient for cheaper ones.

Buying a new helmet

To pass a safety standard such as Europe’s EN 1078, a cycle helmet is strapped to a dummy head and dropped onto a range of anvils to mimic different crash scenarios. Impact forces are representative of a fall from a bike at a modest speed (around 12 or 13mph) with no other vehicle involved. Different parts of the world have different standards. They’re broadly comparable, with only Snell’s B90/B95 standard being significantly more stringent. 

A £100 helmet and a £20 helmet that pass the same tests are certified to offer the same level of protection. However, the expensive helmet is likely to be lighter, better ventilated, more stylish, and possibly more comfortable, perhaps with a fit that’s easier to fine tune. It may also have additional safety features that the cheaper helmet lacks – for example, MIPS.

MIPS stands for Multi-directional Impact Protection System. The internal cradle of a MIPS-equipped helmet is designed to allow the protective shell to rotate 10-15mm in any direction. This is to reduce the rotational movement of the brain in the skull when the head comes to a sudden stop, which can do serious damage.

Helmet fit

Whatever its price your helmet must fit well, both for comfort and so it can do its job. A helmet should not perch on the top or back of your head. The front should be only a couple of fingers’ width above your eyebrows, just visible in the upper periphery of your vision. 

Adjust the helmet’s straps so that: the V-shapes each side meet just below each ear; the chin strap is the right length to buckle snugly but not uncomfortably under the chin. Being able to get your index finger under the buckle is a good guide – and will prevent you nipping skin when you’re fastening a child’s. 

Most helmets have a ratchet strap or dial at the rear to adjust the fit. Do so until the helmet is snug but not uncomfortably tight. Even with the chin strap undone, you should be able to shake your head from side to side and back and forth without the helmet coming loose. (Don’t cycle with the chin strap undone.)

While all helmets are adjustable to some degree, you need to find one that’s broadly your size to begin with. Measure your head with a soft tape measure – across the forehead above your eyebrows, above your ears, and around the back of your head. 

Different head shapes suit different helmets; some are rounder, others longer. So try for fit before you buy or be prepared to take/send it back. An uncomfortable helmet may give you headaches. One that doesn’t fit properly won’t function properly.

You can wear a thin cycling cap, head scarf, or stretchy snood under a cycle helmet to protect your head from the cold, rain, or sun (if so, adjust the cradle and straps as necessary.) Such headgear will make ‘helmet hair’ less severe; although you may still need to spruce up after a commute. A ponytail or plait can be arranged so it escapes under the rear of a helmet.

Helmet extras

Helmets aimed at mountain bikers and day-to-day cyclists tend to come with a detachable peak, which helps keep sun and rain out of your eyes. Those for road cyclists rarely have peak because it would obscure vision when riding with the hands on the drops.

Peaks are detachable for two reasons. The most obvious is that you can choose whether to use it. The second is that the peak should snap free in a crash. Helmets have a smooth plastic outer shell in order to slide and roll better on impact. A helmet that grabs onto the ground could make rotational forces on the brain much worse. A firmly fixed helmet accessory might also be driven into or through the helmet in a crash.

TRL research commissioned by the BBC found that attached cameras didn’t in fact cause the helmets to fail in laboratory tests. However, a helmet that meets a safety standard such as EN 1078 is not required to meet that standard after any accessories have been added to it by the owner.

So think carefully about what, if anything, to add to your helmet – bearing in mind that lights, mirrors, and cameras can usually be attached to the bike (or sometimes the body) instead. How much does the accessory protrude from the helmet? Can it readily break free in a crash? These are risk assessments that you will have to make.

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