How Protective is your MTB Helmet?

Bicycle helmets have been around since the early days of Penny Farthings. Head protection was first constructed from plant material such as pith in the late 1800s before going through radical development in the 1970s. It was Bell who produced the first modern-day helmet, developed with foam and hard plastic. Since then, the helmet design hasn’t changed significantly, but the technology certainly has.

Wearing a helmet is not a legal requirement in the UK, but most mountain bike centres and bike parks enforce a strict no-helmet-no-ride policy and given the nature of this sport, I’m a big advocate of wearing a helmet. When it comes to head protection, there is a huge variety available and with clever (sometimes too clever) marketing manipulation tugging at your purse-strings, it can be challenging to make sense of it all. So let’s break it all down and take a look at the protection inside an MTB helmet and what technology does what.

What is EPS?

Expanded Polystyrene (EPS) has been the staple material in bicycle helmet manufacturing since the 1970s. EPS foam is produced in different densities for different purposes, such as disposable cups and insulation. For bicycle helmets, a higher grade and density of EPS is used to help absorb energy sustained from impact.

To create EPS foam, small polystyrene beads of around 0.5 to 1.5mm are funnelled into a mould where steam is applied to expand the beads by up to 40-times their original size. Through this process, the beads begin to fuse, assuming the shape of the mould. Helmet manufacturers then create a harder outer shell casing, often made from carbon or plastic, to protect the EPS mould and give the product its branded finish. Each brand will have a preferred EPS density to work with, for example, harder EPS foams work well to reduce energy transfer during high-speed impacts, while softer EPS foams are better suited to slower-speed, lower-energy impacts. Some brands have even created dual-density EPS that combine both hard and soft densities.

So, how does EPS foam work inside a helmet? Upon impact, EPS will absorb some of the energy and begin to collapse, which slows down the transmission of energy to your head. However, once those beads collapse, they do not regain their shape, which is why it’s crucial to replace your helmet after a significant impact. EPS-only products are living on borrowed time due to better technology, which is safer, lighter and more breathable.

What is MIPS?

Multi-directional Impact Protection System (MIPS). Developed by Swedish scientists in the 1990s, MIPS technology is a concept based on over 20-years of academic study and research.

The MIPS protection system is designed to reduce rotational energy and forces transferred to the brain from angled impacts. So rather than absorb energy like EPS foam and Koroyd (more to come on that further down), MIPS deflects it. If you have a fall off your bike, your head is affected by both linear and rotational forces. It’s essential to protect your head from both of these forces. However, MIPS concentrates more on the rotational energy from angled impacts, rather than the absorption of it.

The way this technology works in helmets is by inserting a low friction layer between the shell and liner which allows the helmet to slide around the head when impacted. This low friction layer is traditionally grey with bright yellow features, the trademark colours of the MIPS brand. We’re seeing an increasing amount of helmets entering the market with MIPS technology, often alongside its non-MIPS counterpart, giving you a purchasing choice, usually, with a slight increase in retail price for the MIPS insert.

For more information about MIPS Technology, head over to their website here.

What is Koroyd?

When it comes to absorbing energy from direct impact, Koroyd outperforms all other helmet technology. It’s been around for the best part of a decade or so, making its debut in 2014 when Smith Optics incorporated Koroyd into their Forefront MTB helmet. Koroyd has become highly distinguishable with its bright green colour and eye-catching design.

“We are dedicated to creating better helmets. Helmets that are lighter, more durable, more breathable, more sustainable – but foremost – that protect better” – Koroyd

The manufacturing process involves creating small tubes with a copolymer extrusion process, which are then thermally welded together to form a substance that crumples on impact, therefore, absorbing energy. Koroyd explains that during a high-speed impact, their “ultra-light tube structure crumples instantly and consistently on impact, absorbing more force with greater reliability compared to any other helmet technology. This unique behaviour protects the skull and brain from direct and angled impacts, significantly reducing the chance of life-affecting injury.” Extensive scientific research and product development have proven that Koroyd can absorb the maximum amount of linear force from an impact while reducing rotational motion from an angled impact.

This innovative technology puts Koroyd at the front of protection when it comes to absorbing energy in the direction of the impact, whether that’s straight on or at an angle.

Koroyd compressing from impact energy

Skull fractures are directly correlated to the deceleration of the head during an incident which is measured by ‘peak G’ limits. Koroyd helmet safety initiative (KHSI) approved helmets reduce peak G limits to 183G, which is significantly lower than official US and EU safety standards. Pressure on the brain is instigated by two main components of an accident; time and deceleration. Koroyd analyses this using the HIC (Head Injury Criterion) and reduces HIC to 1666 is all KHSI approved helmets.

“Regardless of the impact direction, ultimately linear acceleration is always going to be important. And reducing linear acceleration will also reduce angular acceleration which is a result of oblique impacts.” – Dr Priya Prassad, Ph.D Bio-Mechanics, Wayne State University

Smith Optics was the first cycling helmet brand to adopt Koroyd technology for their Forefront and Overtake models. Today, brands such as Endura, Alpina, Head and Klim also incorporate Koroyd technology into their products. What makes Koroyd the ideal technology to work with is that it’s not only protective, but it’s also much lighter and more breathable than other options. For example, the highly anticipated Endura MT500 full-face helmet is exceptionally lightweight. Weighing a mere 640g, this helmet is the lightest in its class.

For more information about Koroyd, head over to their website here.

What is WaveCel?

WaveCel is relatively new to the MTB helmet market, and its technology is currently exclusive to Bontrager. The concept is that WaveCel can reduce both linear and rotational forces while absorbing energy through a network of mini shock absorbers which sits as a layer between your head and the outer shell of the helmet. When impacted, WaveCel is designed to flex, crumple and glide, while absorbing impact energy and distributing rotational forces.

However, being new to the sports protection industry, other entities have yet to validate WaveCel’s bold claims with further testing. Even for myself, I’m unable to see what’s science and what’s smart marketing – yet.

For more information about WaveCel technology, head over to their website here.

MTB Helmet
Here’s Danny Mac’s Endura MT500 with Koroyd technology.

With EPS foam being the long-standing traditional ingredient for MTB helmets, both MIPS and Koroyd have come along to provide increased protection against linear and rotational forces. However, MIPS technology can only help reduce rotational forces incurred from an impact as its low-friction layer is unable to absorb energy. Whereas Koroyd offers unparalleled energy absorption and thus protection from rotational motion.

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