How to Choose Cycling Helmet. Guide for Triathletes

What are good helmets out there? How to choose the right size bike helmet? Are there any safety considerations when choosing a bike helmet?

For triathletes, a bike helmet is a crucial piece of speed equipment. The right one can feel like a legal draft of air, while the wrong one can leave you overheating and slowed down on race day.

Let’s break down how to find the perfect balance of safety, aerodynamics, and comfort for your needs.

Understanding Helmet Fit and Safety

A bicycle helmet is a single-use impact-management device. It is not designed to be durable; it’s designed to be sacrificial.

The bike helmets consist of two parts:

• The outer shell (usually polycarbonate)

This is the hard, smooth surface. Its job is to spread the force of an impact over a larger area and to prevent punctures and abrasions to your head, for example, from road rash or a sharp rock.

• The inner liner (usually EPS – Expanded Polystyrene foam)

This is the foam that crushes upon impact. By crushing, it absorbs the energy of the impact and decelerates your head more slowly, which drastically reduces the force transmitted to your skull and brain. This foam is designed to crush once. After a significant impact, it is compromised, even if it looks fine.

A poorly fitted helmet is a dangerous helmet. It can shift, twist, or come off in a crash, offering little to no protection.

How to achieve a proper bike helmet fit?

Here are the key points to keep in mind:

• Size

Measure your head’s circumference and use the manufacturer’s size chart. Use a flexible tape measure. Helmets come in S, M, L, or specific centimeter ranges.

• Position

The helmet should sit level on your head (not tilted back) and low on your forehead, about one or two finger-widths above your eyebrows.

• The buckle

The side straps should form a “Y” that meets just under and slightly in front of your ears.

• The chin strap

The strap should be snug against your chin, allowing only one or two fingers to fit between the strap and your chin.

• The retention system (the dial)

This is the dial at the back. Tighten it so the helmet is snug and doesn’t wobble or shift front-to-back or side-to-side when you move your head.

Safety Technologies: MIPS, WaveCel, SPIN, etc.

Traditional bike helmets are tested for straight-on, linear impacts. However, many real-world crashes involve angular or rotational forces. These are extremely dangerous and can cause severe brain injuries like concussions.

Some new technologies address this. These are:

• MIPS (Multi-directional Impact Protection System)

A low-friction layer inside the helmet allows the outer shell to slide slightly relative to the head upon impact, redirecting (shearing) these harmful rotational forces. Very common across many brands.

• WaveCel (by Bontrager/Trek)

A collapsible, cellular liner that flexes and glides upon impact to absorb both linear and rotational forces. They claim it’s 48x more effective at preventing concussions than standard EPS foam.

• SPIN (Shearing Pad INside by POC)

Uses silicone pads placed strategically inside the helmet that deform and slide to reduce rotational force.

Are they necessary? Yes, even though no technology can prevent all injuries, these systems significantly reduce the risk of head injuries from common crash types. They are highly recommended, especially for high-risk riding like mountain biking.

Types of Bike Helmets

Bike helmets come in various designs, each optimized for a specific type of riding. The main differences lie in their coverage, weight, ventilation, and aerodynamics.

Here are the main types of bicycle helmets, broken down by discipline.

1. Road Bike Helmets

These helmets are designed for speed, efficiency, and maximum cooling on paved roads. They are best for road cycling, racing, long-distance riding, and gran fondos.

Key features include:

• Excellent ventilation. Many large, well-designed vents to keep airflow high and the rider cool during strenuous effort.
• Lightweight. Constructed from advanced materials like EPS foam and polycarbonate shells to minimize weight.
• Aerodynamic designs. Many modern road bike helmets feature a sleek, teardrop shape to reduce wind drag, sometimes at a slight cost to ventilation.
• Visor. Typically, road bike helmets do not have a built-in visor to allow for wearing sunglasses and maintain an aerodynamic profile.

2. Mountain Bike Helmets

Mountain bike helmets are built for protection and durability in off-road environments where impacts with trees, rocks, and falls are more likely.

There are several sub-types of mountain bike helmets, such as:

• Cross-country (XC) helmets look similar to road helmets but with a visor and slightly more rear coverage. They are lightweight and well-ventilated.
• Trail/enduro helmets offer more substantial coverage and protection for aggressive trail riding and enduro racing.
• Full-face bike helmets provide the maximum protection. They cover the entire head and feature a chin bar. These helmets are essential for downhill (DH) riding and bike parks.

Key features of mountain bike helmets include:

• Increased coverage. Provides more protection for the back of the head compared to road helmets.
• Visor. Almost always includes a fixed, protruding visor to shield the eyes from the sun, rain, and tree branches.
• Robust construction. Often built to withstand more abrasive impacts.
• Goggle compatibility. Designed to work seamlessly with MTB goggles, which may include a dedicated channel in the rear.

3. BMX / Skate-Style Helmets

These are “hard shell” bike helmets designed for repeated impacts, similar to skateboarding or rollerblading. They are best for BMX racing, BMX freestyle (park, street, dirt jumping), skateboarding, and scooter riding.

Key features include:

• Durable hard shell. Made with a tough ABS plastic outer shell that is highly resistant to scratches and multiple small impacts.
• Round, uniform shape. Provides protection from any angle, which is crucial for the types of falls common in BMX and skateboarding.
• Minimal ventilation. Usually have few or no vents, as they prioritize durability over cooling.

4. Aerodynamic Helmets / Time Trial Helmets

Time trial bike helmets are highly specialized helmets designed for one thing: minimizing aerodynamic drag. As the name implies, these are used for time trials, triathlons, and road races where every second counts. They are not practical for general use.

Key features include:

• Slick, tailed design. Features a long, smooth “tail” to cover the dead air space behind the head and allow air to flow cleanly off the rider’s back.
• Minimal vents. Vents are often closed or non-existent to keep air from swirling inside the helmet, which creates drag. This makes them very hot.
• Face shield. Many integrate a full visor or shield to streamline the transition from head to face.

5. Full-Face Helmets

Full-face bike helmets offer the maximum protection available as they enclose the entire head.

These bike helmets are best for downhill mountain biking, freeride and enduro, and BMX racing. They are also often required for gravity park riding.

Their key features are:

• Chin bar. This is the defining feature that protects the jaw and face.
• Heavyweight. Significantly heavier than open-face helmets due to the increased material.
• Reduced ventilation. While modern designs have improved airflow, they are still hotter than other types.

Top 5 Helmet Brands for Triathlon

For a triathlete, the choice of helmet is heavily weighted towards aerodynamics. The goal is to minimize drag to save every possible second, often at the expense of maximum ventilation. The top brands are those that have invested heavily in wind tunnel testing and innovative design specifically for the time-trial position.

Here are the top 5 helmet brands for triathlon, known for their performance, innovation, and prevalence on the race course.

1. Giro

A perennial leader in both road and aero helmets, Giro is arguably the most popular and trusted brand in triathlon. They combine proven aerodynamics with practical features and a range of price points. Their bike helmets are trusted among triathletes around the world.

Here are a few models to look at:

• Flagship Model: Giro Aerohead (and Aerohead Ultimate)

This is the iconic “head sock” helmet that has been worn by countless age-groupers and pros (including Jan Frodeno) to victory. It’s a long-tail design focused on pure aerodynamic efficiency.

• Other Key Model: Giro Empire

A more versatile “do-it-all” aero road helmet that offers excellent aerodynamics without the extreme length of a pure TT helmet, making it a great choice for athletes who want one helmet for training and racing.

2. Specialized

Specialized applies its “Win Tunnel” data-driven approach to everything it makes, and its TT helmets are among the best in the world. They are known for meticulous design and integration with the rider’s position. The asymmetric design is a truly innovative approach to real-world aerodynamics.

Take a look at their flagship model: Specialized TT5 (formerly S-Works TT)

• This helmet is the product of immense R&D. It features a unique asymmetric design that accounts for the fact that a rider’s head is often turned slightly to one side while in the aero bars. It’s a top choice for pros seeking every marginal gain.

3. Kask

Kask bike helmets are instantly recognizable for their impeccable Italian design, premium materials, and superb comfort. They are the helmet of choice for the Ironman Pro Series and many top pros.

They offer superior build quality, comfort, and padding. Plus, the partnership with Ironman makes it the most common helmet you’ll see on the pro tour.

What to explore at Kask:

• Flagship Model: Kask Utopia

Designed in collaboration with Team INEOS Grenadiers, this helmet is a masterpiece of combining aerodynamics with exceptional ventilation via its active vent system. It’s a favorite for athletes racing in hot conditions who don’t want to sacrifice all cooling for aerodynamics.

• Kask Protone Icon

While more of an aero-road helmet, its performance is so strong that many triathletes use it for racing. They mention that these are some of the lightest helmets out there.

4. Rudy Project

Rudy Project has a deep history in triathlon and is famous for its highly customizable and adaptable helmet ecosystem. They offer a wide range of fit and accessory options. Customization and the integrated visor system. The “one-and-done” solution for athletes who don’t want to deal with sunglasses.

Their flagship model is Rudy Project Wing55.

This helmet is engineered specifically for the needs of triathletes. Its key feature is the integrated magnetic eye shield that stows cleanly away, eliminating the need for separate sunglasses. It’s also designed to work with their optional AeroBrow and AeroTail accessories to fine-tune aerodynamics for your specific position.

5. MET

MET has made huge strides in aero technology with a focus on combining low drag with excellent ventilation. Their designs are often based on groundbreaking concepts.

The brand offers innovative and often bold design choices backed by solid engineering. They offer top-tier performance that competes directly with the biggest names.

Their flagship model is MET Drone.

This is a pure-bred, long-tail TT helmet designed for absolute speed. It features a NACA duct-inspired intake and internal channels to manage airflow and reduce drag, claiming to be one of the fastest on the market.

When to Replace a Helmet?

You might think that a small crack is not a reason to buy a new helmet, but it actually signals that the helmet’s energy-absorbing foam has been damaged and can no longer be trusted to perform as designed. Here is when you should replace your helmet:

• After ANY crash. If you hit your head, the EPS foam has likely compressed. Replace it immediately, even if you see no damage.
• Every 3-5 years. The materials (especially the foam and straps) can degrade over time due to exposure to UV light, sweat, and temperature changes. The manufacturing date is often stamped on a label inside the helmet.
• If it’s damaged. Look for cracks in the shell, compression or crumbling of any foam, or frayed straps. If in doubt, replace it.
• If it no longer fits correctly, this is especially important for children.

The Importance of Bike Helmet Testing and Certification

Always look for a certification label inside the helmet. This means it has passed rigorous safety tests for your region.

In the US, look for CPSC (Consumer Product Safety Commission)certification. This is the mandatory standard.

In Europe, check for CE EN 1078. This is the standard for adults, and EN 1080 is for children (with a breakaway feature to prevent strangulation).

In the UK, the UKCA mark (largely identical to CE standards) is mandatory.

In Australia and New Zealand, check for AS/NZS 2063 certification.

Some helmets may also have more stringent voluntary certifications like ASTM F1952 (for downhill mountain biking) or Snell B-90/B-95.

Keep in mind that a helmet without a recognized safety certification is a toy, not protective gear.

What is the Virginia Tech Helmet Lab?

When researching bike helmets, you most probably will come across the Virginia Tech Helmet Lab. So, what is it and why should you trust this source?

This is a research team within the Virginia Tech School of Biomedical Engineering and Mechanics, led by Professor Stefan Duma. They are originally focused on military and football helmet testing. The Virginia Tech Helmet Lab famously applied its rigorous scientific methodology to bicycle helmets starting in 2016.

Their mission is to reduce the risk of brain injury by providing independent, evidence-based ratings of helmet performance.

What Makes Their Approach Different?

Before the Virginia Tech Helmet Lab, most consumers only knew if a helmet passed the mandatory government safety tests (like the CPSC standard in the U.S.). The Lab’s key innovation was creating a 5-Star STAR Rating System that allows helmets to be compared based on how effectively they reduce brain injury risk.

Their testing is considered more comprehensive and realistic than the standard pass/fail tests because:

1. They test for rotational force. Traditional standards primarily test for linear impacts (straight-on, crushing forces). Virginia Tech’s tests also measure a helmet’s ability to reduce rotational acceleration (the twisting and shearing motion linked to concussions and more severe brain injuries).
2. They use a wider range of impact scenarios. They test each helmet at multiple impact speeds and at six different locations (front, side, rear, etc.), simulating a variety of real-world crash scenarios.

How to Use Their Ratings

Their website is a powerful, free tool for consumers.

1. Go to the official website
2. Navigate to “bicycle helmets”. You’ll find a list of all the helmets they have tested.
3. Sort and filter: You can sort helmets by their STAR Rating (5-star is best), by type (Road, Mountain Bike, Urban, etc.), and by price.
4. Make an informed choice. The top of the list will show you which helmets their testing has shown to be the most effective at reducing brain injury risk.

Checklist for Choosing the Best Bike Helmet

Use this list to make sure you’ve got all your bases covered.

Step 1: The Non-Negotiables (Safety Features)

✅ Certification Stamp. Look inside for the safety certification label required for your region.

✅ Rotational impact tech. Look for and prioritize helmets with proven technologies like MIPS, WaveCel, SPIN, or similar. This is no longer a “nice-to-have” for major brands, but a critical safety layer.

✅ Condition check. Is it new or undamaged? If you’re replacing an old helmet, remember: any crash, any major drop, or helmets over 5 years old need to be retired.

Step 2: Fit & Feel

✅ It should feel right for your head shape and cover your forehead without obscuring your vision. The cycling cap must feel secure without giving you a headache.

✅ Once buckled, can you shake your head “no” vigorously without the helmet wobbling? If it shifts easily, it’s too big.

✅ The front rim should be one or two finger-widths above your eyebrows. The side straps should form a “Y” under your ears. Only one or two fingers should fit under the chin strap.

✅ Use the rear retention dial to fine-tune the fit. This is what locks everything in place.

Step 3: Type & Features

✅ Are you getting the right type of helmet?

• Road сycling: Lightweight, well-ventilated, often aerodynamic.
• Mountain biking: More coverage, visor, often a tougher build. Consider full-face for downhill.

✅ Does it have enough vents to keep you cool on your typical rides? More vents usually mean more cooling, but can sometimes mean less aerodynamics.

✅ A lighter helmet is generally more comfortable on long rides.

Step 4: The Final Once-Over

✅ Is it a bright color? Does it have reflective elements or provisions for lights? Being seen is a key part of safety.

✅ Is the padding moisture-wicking and removable for washing? Are the straps soft and adjustable?

✅ You’re more likely to wear a helmet you’re happy to put on. Does it look good and feel good to you?

Tri-helmet or aero road helmet?

This is a popular discussion among triathletes. The thoughts might differ, but for the vast majority of triathletes, the aero road helmet is the smarter choice.

The performance penalty is minimal, especially when compared to the massive benefits of versatility and comfort. The marginal gains from a full TT helmet can be easily negated if you have to sit up due to overheating.

Final advice from the trithalon community: Unless you’re a top-level competitor where a minute truly matters, invest in a high-quality aero road helmet. You’ll get 95% of the aero benefit and 100% of the usability.

Helmet Maintenance Tips

Proper maintenance is crucial for keeping your helmet safe and performing as intended. Follow these key steps:

1. Use a soft cloth, mild soap, and lukewarm water to clean the shell and straps. Avoid harsh chemicals, solvents, or abrasive cleaners that can degrade materials.
2. Always air dry the helmet away from direct heat sources like radiators or hair dryers. Excessive heat can damage the EPS foam liner.
3. Before each ride, perform a quick visual and tactile inspection. Look for any hairline cracks, dents, or deformities in the outer shell. Check the interior foam for any compression or crumbling.
4. Ensure the straps are not frayed and that the buckles clip and unclip smoothly. Replace the entire helmet if any part of the retention system fails.
5. Keep your helmet in a cool, dry place away from direct sunlight. UV radiation can weaken the plastics and foam over time. Avoid leaving it in a hot car.
6. Don’t drop your helmet onto hard surfaces. While it may not seem like a big impact, it can create micro-fractures in the foam that compromise its ability to absorb a major impact.

When your current helmet reaches the end of its life, typically after 3-5 years or any impact, it is time to research the latest best road bike helmets from trusted sources and brands.