The short answer here is no. Or at least it definitely isn't recommended. This is for a few reasons; a collision on the road is different from a crash on an awkward and unforgiving steep hill.
A mountain bike helmet provides more protection around the head, and the two helmets are designed with two completely different purposes in mind. Yes, both will be designed to standards, and both are designed to protect your head, but under very different circumstances.
In all honesty, when I started out mountain biking a few years back, I came from a road cycling background. I had all the gear for road cycling, but only had a bike for mountain biking. I rode with a road helmet for a few months as I figured I didn’t really need anything too special as I wasn’t any good at mountain biking at that stage. I had it in my head that I probably wouldn’t come off until I was riding the black diamond trails.
How wrong was I? I did come off, just a small crash, and hit the back of my head. It was at this point that I realized how incredibly exposed the rear of my head was to any crash. From that point on, I have always used a mountain bike helmet for mountain biking.
As annoying as it is to have to purchase duplicate gear when you are a multi-discipline cyclist, it is a necessity. No, it is not just the cycling industry trying to get twice the amount of money out of you, it really is a matter of health and safety. Here is my explanation as to why you need a mountain bike helmet for mountain biking.
Although not recommended, if you are just riding dead flat trails with no surprises, gravel roads, or just around town, a road bike helmet would do the trick. Anything a step up in difficulty from this, more protection will be required.
What is the Difference Between a MTB Helmet and a Road Bike Helmet?
There is a big difference in what a mountain biker and road biker look for in a helmet. This is mostly down to how they ride and more importantly how they crash.
What Road Bikers Look For
A road cyclist prioritizes speed. A road bike helmet is designed to be aerodynamic, lightweight, and designed with as much ventilation as it can allow while still offering protection in a crash.
A road cyclist will spend significant money and time on ensuring their gear is lightweight and aerodynamic as possible. This is done to reduce the amount of energy the cyclist has to exert, as at high speeds, more resistance means a lot more effort required from the cyclist. Effectively, the helmet is made as minimalist as possible while still meeting safety codes.
A research survey conducted by The Princess Royal Hospital showed that 87% of cycling-related injuries were caused by off-road riding, indicating crashes were far more prominent in mountain biking than road cycling check out the full paper here.
What Mountain Bikers Look For
A mountain biker prioritizes safety. Mountain bikers rely a lot less on the aerodynamics of the set-up, and more on the skill and lines that the rider chooses for speed. As the riding becomes faster and more difficult, mountain bike helmets have to increase protection.
Speaking from experience, mountain biking involves a bit of crashing, particularly when you are starting out on the technical terrain and don't quite have enough speed to make it over a few of those rock gardens. Companies design helmets to exceed safety requirements, there have been improvements in anti-rotational systems, and greater protection around the head for the just-in-case scenario.
But won't my head still be protected if I crashed?
A 'design crash' on a road bike is a high-speed forward-moving crash on the pavement, so the construction of a road helmet is designed for a slide across the pavement. A mountain bike crash tends to be a lot more awkward due to the typically rough and challenging terrain, and the helmets are designed to protect against this.
The mountain bike helmet has more coverage, particularly around the rear of the head. This is for two reasons,
1) It is possible that a rider may flip over or take a knock to the back of the head, or
2) The helmet protects the rear of the head from sharp rocks or other objects that could harm the head.
Difference in Construction
There is actually a difference in the way the two different helmets are constructed. A typical road bike helmet will be constructed using in-mold technology. The in-mold technology is a lighter weight style of binding the foam layer to the outer shell.
A mountain bike helmet will have a hard shell that is attached to the EPS liner with strong glue. The shape is clearly different, with a mountain bike helmet protecting more of the sides and rear of the head, with fewer vents than a road helmet. With fewer vents, there is less material to protect your head, so the material has to be made much harder to offer the same amount of protection in a crash. By making the material harder, this increases the force transferred to the head-on impact, which may be fine in a road crash, as it is usually more of a slide across the pavement, which requires hard materials anyway. However, it would not be a comfortable crash on mountain biking terrain where you might come to an abrupt stop because you have hit a tree, for instance.
The difference in construction does make a big difference in the protection on your head and has the potential to be that defining factor in whether it saves your life or not.
Does a Mountain Bike Helmet Actually Give a Rider More Protection than a Road Helmet?
Yes, just look at the profile of a mountain bike helmet next to a profile of a road bike helmet. A mountain bike helmet has significantly more coverage, and more coverage will mean more protection. An awkward fall from a mountain bike could have you hitting the rear of your head on a hard rock or root, which would be prevented by wearing a mountain bike helmet, but not so with a road bike helmet.
The much larger vents on a road bike helmet also leave your head vulnerable for sticks to poke through, whereas a mountain bike helmet will be designed to reduce the chances of this occurring. Both helmets give you the option to have anti-rotational systems (such as MIPS) and having these systems are equally as important in both disciplines.
Other Features that make Purchasing a Mountain Bike Helmet a Worthwhile Option
Aside from greater protection, a mountain bike helmet will usually feature a few additions which help while riding.
A visor will shield the rider's eyes from glaring sunlight while riding in dappled light, potentially reducing the chances of hitting something unwanted or crashing.
The visor is often adjustable for when the sun is high or low, and some will be designed to break away in the event of a crash, so the visor doesn't interrupt the motion on the ground. For more on mountain bike helmet visors check out our article on why MTB helmet visors exist.
Whereas for a road cyclist, having a visor would limit vision while riding due to the position on the bike, not to mention the reduction in aerodynamics!
Mountain bike helmets usually feature goggle compatibility which is a grove which allows your goggle strap to sit in. This keeps them secure on your helmet and prevents them from slipping off. Most mountain bike helmets also have a light and camera mount which is very useful for recording you shred out in the trails.
Can you use a Mountain Bike Helmet for Road Biking?
We have established that the two helmet styles have very different purposes, but in saying that, a mountain bike helmet does provide more protection. If you aren't going for speed, or don't mind having a visor in your vision (some prefer it as it blocks the sun), there isn't really any significant safety reasons not to. A few points to consider would be that;
- A visor reduces aerodynamics significantly and may get in the way in a high-speed crash, potentially causing your head to have an awkward angle while crashing
- Mountain bike helmets have significantly less ventilation, so it may get a little warmer while riding on the tarmac, especially as the tarmac heats up.
- The mountain bike helmet, due to having more coverage and protection, will also be a bit heavier, which becomes noticeable in the aerodynamic road riding position.
If you aren't a high-speed racer and don't feel inclined to purchase a second helmet for your road riding, a mountain bike helmet will be sufficient. If you are in the process of buying a mountain bike helmet and intend to use it for both disciplines, we would recommend the following;
- Purchase a helmet with a breakaway visor, so if you crash, the visor will break off and won't cause your head or neck to bend at obscure angles.
- Alternatively, a helmet with a removable visor so you can ride visor-less on the road, and with a visor on the trails
- Purchase a helmet that is lightweight and provides plenty of ventilation.
- The helmet must still protect the rear of the head in case of a crash on the trails.
Helmets that can be used for Both Road and Mountain Biking
If you don't want to spend that extra amount on two types of helmets, the helmets below are a great choice. They offer sufficient protection and features for both disciplines making them great all round helmets.
Not only it the Axion an extremely stylish helmet with well above standard protection, but it also has a breakaway visor to keep your head safe. It also features POCs unique airflow channels that will keep your head cool, even when road biking on hot summers days.
This helmet allows you to detach and reattach your visor as you please, which is very handy if you are constantly switching between the two disciplines. It features an in-mold construction, which reduces the weight of the helmet, and a Roc Loc Sport fit system for greater comfort.
If your budget allows purchasing two helmets is definitely worth it to protect your head. That being said the two helmets that have features that make them suitable for both road and mountain biking are a great alternative for tighter budgets. They offer more protection than a standard road bike helmet, but still have many of the key features such as breakaway visors and good air flow.
These are professionals that are designing helmets. They have had many years of refining designs to increase the safety of riders. In my mind it is a no brainer, I would happily make a small purchase in order to keep my skull and brain from unnecessary harm. You just can't put a price on safety!
If you are wondering when to replace a bike helmet, check out our in-depth discussion here.