Buying Advice - Bicycle Helmets
HOW A HELMET WORKS
The primary function of a bicycle helmet is to cushion the head during an impact with a hard object, rather than to enclose the head in a strong "case". Wearing an immensely strong helmet might do a good job of keeping the head looking like a head, but unless it also cushions the impact, brain damage can still occur. This is because when the head comes to an instant stop, the brain might not; it might slosh about within the skull slightly. That's not good for it.
Bicycle helmets supply this cushioning effect by using a thick layer of expanded polystyrene, which crushes on impact. This gives the head a couple of centimetres in which to slow down, hopefully preventing the sloshing effect.
Helmets have some sort of cover over this expanded polystyrene layer. This is primarily to hold the polystyrene in place, even if it's broken into several pieces, in case of further impact.
Helmets also have some sort of retention strap system to keep the helmet on the head.
WHAT TO LOOK FOR
Fit - The most important thing a helmet has to do is to stay where it belongs. An accident can involve more than one impact for the head, and a close fitting helmet is more likely to stay put during an accident, providing protection in case of further impact.
Fit - A close fitting helmet also spreads the contact area between the head and the helmet, reducing peak pressure.
Fit - A helmet that fits will be comfortable to wear. A helmet should fit snugly but without squeezing the head. A helmet that is too large, although it might feel comfortable when first tried on in the shop, will be more noticeable while riding as it will be shifting on the head when riding over bumps, and can possibly more so far forward that it obstructs vision, or so far back that it offers no protection to the forehead.
Fit - Do you think we're over emphasising the point? Fit is made up of several factors: helmet size, helmet shape, interior padding, retention system and retention system adjustment. See below.
Shape - Some helmets suit narrow heads, some suit wide heads. We had a helmet a few years ago that fitted cone shaped heads, but there wasn't a big market for that one and it's no longer available.
Retention Straps - All helmets use essentially the same system of 2 sets of straps coming down from the helmet and meeting at a junction below the ears and contunuing down to a buckle under the chin. These sets of staps can be free floating in the helmet, or one or both can be fixed. I like fixed staps as they stop the junctions from ending up in funny places when the helmet is fitted. The cheapest helmets often have both sets of straps free floating, but there are several top quality helmets that are also like this.
Locking Strap Length Adjustment - Once the helmet straps are adjusted, you want them to stay that way. One simple feature a helmet can have is a rubber O-ring around the straps near the attachment buckle. This is not to keep the escess straps tidy, it is to prevent the excess straps from slipping back through the buckle, loosening the fit of the helmet. Of course, a rubber band will do the job nicely on a cheaper helmet.
Locking Junction Position - The front pair of straps and the rear pair of straps should meet just below the ear, and the straps should not cover the ear. This is achieved by moving the position of the junction of the two sets of straps and adjusting the length of each strap above the junction. The helmets are easy to adjust when the straps move easily through the junctions, but they'll also go out of adjustment easily when the helmet is used if the junctions do not lock the straps in position. Good helmets will often have junctions that allow for easy adjustment, and then lock the straps in so the adjustment stays put.
Ventilation - Riding fast on a hot day is hot work. A poorly ventilated helmet will soak your head in sweat, and can cause loss of concentration. Generally, as helmets get dearer, their ventilation improves.
Shell Type - Most helmets now are made with a microshell, that is, a thin plastic shell over the expanded polystyrene. Helmets were originally made with a hard shell, making a heavier helmet that could withstand rough treatment for longer. Hard shells are still used on skate helmets which are subject to more frequent small impacts. In order to save weight, helmets were then made with a soft shell, or lycra cover. These did still keep the pieces of a broken helmet in position on the head, but they had three faults. (1.) They were prone to coming off the helmet altogether, whether during an accident or two years before. (2.) They also resulted in a helmet that gripped the road too well, increasing the chance of neck injury. (3.) They restricted airflow through the ventilation holes, making the helmets hotter. And, for good measure, (4.) They faded terribly. The latest type of shell is the in-mould shell, more often referred to as in-mould construction of the helmet. These are good, so they're covered in the next point.
In-Mould Construction - These work like reinforced concrete, which gets its strength by combining the strength of steel with the bulk of concrete. In-mould constructed helmets start with a strong outer shell (a bit thicker than microshells but not as thick as hard shells) and then have the polystyrene pumped into them, forming a single piece. The combination of strong shell bonded to a bulky polystyrene layer gives a helmet that's very strong. This could be of adventage in a crash involving an uneven surface. An in-mould constructed helmet is also better able to withstand the knocks and bumps of general handling, so are likely to outlast other helmets.
Skirt - All helmets have a shell over the polystyrene on the top part of the helmet, but most leave the polystyrene base exposed. This means the base will scuff and dent easily. Some helmets come with a protective skirt, either in a taped on microshell, or a stronger in-mould shell. These helmets will handle life's bumps and scrapes well.
Visor - Visors are great for keeping the sun out of your eyes, for keeping branches off your face when riding in the bush, and for keeping the glare of car headlights out of your eyes when riding at night. Helmets with visors are often called mountainbike helmets, and helmets without visors are called road helmets. Don't blame us! A few years back there were a few quite large visors about, but they tend to obstruct vision. A fairly small visor, attached fairly high on the helmet seems the best.
Head Lock - There are many names for these, including Rok Lok, Head Lock, Full Nelson, Half Nelson, etc. They're all variations on two basic themes: (1.) Adding an adjustable strap that grips the back of the head under the occipital bone (the bump on the back of your head) and (2.) Lowering the attachment point of the rear retention straps, making the helmet more difficult to push forward on the head. These make the helmet grip the head rather than just sit on top. They make for a more comfortable helmet, one that doesn't move about over bumps. The better versions will also help keep the helmet in place during an accident. They vary in quality and effect.