To start with, we will have a look at what makes a good helmet in the first place. There are a lot of technical terms thrown about, with little understanding of what they actually mean. For example, many helmets advertise an 'EPS Liner/Inner' and a Polycarbonate shell, but what are these, and are they right for you?
What Makes a Good Helmet?
The whole idea of a helmet is to protect your head after a crash, minimizing or negating the impact so that your head does not suffer any physical impact or brain injury. However, since the majority of the time you won't be crashing (hopefully), a good helmet should also be comfortable for riding.
So what suffices as good protection? A helmet is typically made of two components- the outer shell and the inner liner.
The outer shell, the plastic outer material that you see, has two main functions:
- To help stop sharp objects from penetrating through the helmet
- To allow your head to skid safely across the ground surface without bending your neck (given no objects are in the way).
What to look for:
- Polycarbonate Plastic is by far the most dominant mountain bike helmet material on the market. It is a very tough, lightweight, durable material so very commonly used on helmets.
- ABS (or Acrylonitrile Butadiene Styrene) is another commonly used plastic, very similar properties to the Polycarbonate, but slightly heavier. Still an excellent option, and usually slightly cheaper.
- Carbon Fibre is more commonly used on Full Face mountain bike helmets. It is still reasonably lightweight and has very high protective capabilities.
The inner liner is the 0.4-0.8 inches of foam beneath the outer shell, which forms the bulk of the helmet. Fundamental physics states that a force will be dissipated more if the duration of the impact is longer. The foam layer crushes on impact, increasing the stopping time, which significantly reduces the severity of the impact. An ideal liner would be lightweight, breathable, cost-effective to shape and produce, harden on hard impacts, and soften on softer impacts to reduce the severity of head injuries.
What to look for:
- EPS (Expanded Polystyrene): EPS, the trademarked brand of Styrofoam used in helmets, is the most common inner liner on the market and for a good reason. It dissipates the energy from an impact exceptionally well and is relatively inexpensive to form the internal of a helmet. However, it is only suitable for one crash, which is the reason experts recommend replacing your helmet after a single impact.
- EPP (Expanded PolyPropolyne): Works to a similar effect of the EPS, but is slightly heavier and bulkier. However, it can work as a multi-impact material, so the helmet can take up to a few blows before needing to be replaced. It is not yet as commonly used as EPS due to costs and weight increases, but manufacturers are working on blending the two materials to make the ideal liner. The EPP and EPS blend is more common in full-face helmets than a half-shell, as weight is less of a consideration.
An anti-rotational system is one that reduces the rotational movement of your brain during a crash. It is the rotational movement that is said to cause brain damage during a collision. Many anti-rotational systems have appeared on the market in recent years, and the sheer number of these can be overwhelming for someone looking for improved protection. Below we have explained the more conventional systems.
- MIPS: A low friction layer, which is separate from the EPS layer. In basic terms, the MIPS component allows the helmet to move during a crash without rotating your head. This means that during an angled crash, there is less rotational movement transferred to your brain.
- SPIN (by POC): Spin pads are placed in specific locations inside the helmet to prevent oblique or rotational impacts by shearing in any direction. SPIN stands for Shearing Pads Inside. The pads are constructed of highly protective medical-grade silicone, and very comfortable.
- 360 Turbine (by Leatt): These are disc-shaped pads that harden on impact. They act to dissipate rotational direct and deflective impact energy. The discs are placed strategically within the helmet to protect temples and vulnerable parts of the head. The turbines are non-Newtonian turbines that spin and deform to absorb energy.
- WaveCel: Wave cell supplements the EPS layer of the helmet. They are effectively a grid of waves that offer protection from angular crashes. Supposedly better than MIPS at reducing speed, and hence the severity of the impact, but scientifically proving this is very difficult.
- Koroyd: In simple terms, Koroyd is made up of many small collapsible thin-walled tubes that are welded together to form a lightweight, breathable core of the helmet. It effectively looks like thousands of small straws put together, making a large crumple zone and reducing the rotational movement of the head.
MIPS, SPIN, and 360 Turbine have very similar approaches to reducing rotational movement by adding a liner to the existing EPS layer and are all very effective options for protection. WaveCel and Koroyd have taken a different approach, by integrating the EPS layer with anti-rotational systems, to make it lighter and to have supposedly better crumple zones, which you do pay slightly more for. Check out our pick of the best MTB helmets with MIPS.
But which is better? Each system claims they are better than the previous, but there has been little hard evidence into which the system is more effective. However, each system does have to meet certain standards, so you can rest assured that any technology you choose will be a big step up from just the standard foam layer.
You will be wearing the helmet for every mile of every ride, so you want it to be comfortable. A comfortable helmet is one that is lightweight, with good ventilation, and fits the head snugly without compromising on safety in any way. You don't want the helmet to be uncomfortably tight, but one that won't move around on your head if you give it a violent shake.
Adjustable Sizing: Good features include adjustable sizing- such as an adjustable wheel- which allows you to tighten or loosen the helmet once it is on your head.
Ventilation: Having good ventilation enhances wind flow between the helmet and your head, keeping you cooler and hence more comfortable. More vents will typically also correlate to a lighter helmet too!
Visor: Most mountain bike helmets will come with a visor to shield your eyes from the sun while shredding in the park. Having the sun in your eyes, particularly if you are heading through trees and get a flash of sun every few moments will never be comfortable! For more on visors, check out our deep dive into MTB helmet visors.
Moreover, there are some additional features you may want to consider.
Goggle Compatibility: Helmets can offer goggle compatibility, which gives you a space on the helmet to rest your goggles without them slipping off. Particularly useful if you choose to take the goggles off to ride certain sections and want them resting upon the helmet.
Camera or Light mount: Some helmets have a design that allows you to mount a light or camera to allow you to capture your riding. The mounts are typically sold separately, but the design which allows for the mount to be added can be beneficial, especially if you intend to do any riding in the dark. If you are looking for helmets with built in camera mounts, check out our top 8 picks.
Chin Bar: The chin bar is a feature on Downhill helmets. It provides more protection for the front of the face and chin in case of a crash. The chin bar can be removable on some helmets, reducing the weight for uphill climbs and easily re-attachable for the downhill section. Check out our top picks for convertible helmets. Only really required for advanced downhill riding or racing, as it does add significant weight and less ventilation to a helmet.
So how to choose the right helmet for you?
Your style of riding dictates the amount of protection, level of comfort, and additional features you will be requiring. For example, someone riding a short, flat gravel trail is requiring less protection and additional features but may desire greater comfort than someone riding advanced downhill trails.
In terms of cost, you will pay more for greater protection, lightweight materials, good ventilation, stronger materials and construction, style, comfort, and additional features. Decide which of these factors will be more important to you and work from there.
Find out more about our picks for the best low profile helmets here.
If you want to find out more about when to replace a bike helmet, check out our guide here.
If you need more help in deciding which style of helmet to look for, see here: What are the different types of Mountain Bike Helmets.