What are Bike Helmets Made of?

Founder, Mr. Mamil

Choosing the right bicycle helmet is more than just a matter of style or price point; the materials used in helmet construction play a critical role in both safety and comfort.

The helmet shell, liner, padding, and retention system contribute to the helmet’s overall performance, with different materials offering unique advantages and considerations.

In this article, I’ll compare the most commonly used materials in each of these four key helmet parts; exploring Polycarbonate and ABS for shells, various liner materials, padding options, and the materials employed in retention systems.

By understanding these, you’ll be better equipped to decide which helmet is right for you, balancing your specific needs and preferences for safety, comfort, and durability.

Polycarbonate vs ABS shell

The helmet shell is critical, protecting the head from impact and abrasions. Helmet manufacturers choose specific materials for the shell based on factors such as strength, weight, durability, and cost.

CharacteristicPolycarbonate (PC)Acrylonitrile Butadiene Styrene (ABS)
Type of helmetsRoad, time-trialMountain bike, downhill, commuter, kids
Helmet price$$$ – $$$$$$ – $$$
Raw material costAffordable, roughly $1.50/lbAffordable, roughly $1.50/lb
RecyclabilityCan be easily recycled at specific facilitiesCan be easily recycled at specific facilities
Impact ResistanceHigh, making it ideal for protecting against head injuriesExtremely high, offering excellent protection
Heat ResistanceUp to 176ºF/80ºCUp to 266ºF/130ºC
Cold ResistanceDown to -4ºF/-20ºCDown to -40ºF/-40ºC
Chemical ResistanceGood, helps in maintaining the helmet’s integrityGood, ensuring the helmet’s durability
UV ResistanceFair, but may degrade with prolonged sun exposureBetter, though still may weaken over time
WeightLightweight, contributing to comfort during long ridesHeavier, which could reduce comfort on long rides
VentilationCan be molded to include vents, improving airflowGenerally fewer vents, leading to less comfort during warm rides
Aesthetic AppealShiny and resistant to scratches, maintains a good appearanceCan get scratched, affecting the overall look
Comparison between PC and ABS shell characteristics in bike helmets

Here is a more detailed explanation of the common shell materials.

Polycarbonate (PC) shell

Polycarbonate, a thermoplastic polymer known for its high impact resistance, is a popular choice for helmet shells.

Its lightweight nature, excellent optical clarity, and ease of molding into various shapes make it ideal for helmet construction. Often used in in-mold construction, polycarbonate bonds well with EPS liners during manufacturing. Its affordability and versatility make it suitable for a range of helmet designs, from entry-level to high-end models.

Pros of PC shell

  • High impact resistance. Polycarbonate provides a strong and protective outer shell, effectively absorbing and dispersing the force of impacts.
  • Lightweight. The material’s lightweight properties contribute to a comfortable, easy-to-wear helmet.
  • Cost-effective. Polycarbonate is an affordable option for helmet manufacturing, making it accessible to a wide range of cyclists.
  • Compatibility with in-mold construction. The ability to bond well with EPS liners during the in-mold process results in a seamless, integrated helmet design.

Cons of PC shell

  • Susceptibility to scratches. Polycarbonate can be prone to scratches, affecting its appearance and potentially compromising its optical clarity.
  • UV degradation. Prolonged exposure to sunlight may cause the material to weaken or discolor, impacting the helmet’s durability and appearance.
Examples : Lazer G1 MIPS, Kask Protone, POC Ventral Air SPIN

Acrylonitrile Butadiene Styrene (ABS) shell

Acrylonitrile Butadiene Styrene (ABS) is a thermoplastic known for its toughness and rigidity.

Boasting a higher tensile strength than polycarbonate, ABS contributes to the durability of helmets. Often used in skate-style helmets and budget-friendly options, ABS provides a hard, protective outer shell at a lower cost. However, ABS plastic is generally heavier than polycarbonate, making helmets less comfortable for long rides.

What is ABS plastic?

Pros of ABS plastic shells

  • High tensile strength. ABS offers a strong, rigid outer shell, enhancing the helmet’s overall durability.
  • Durable. The material’s toughness makes it resistant to cracks and other damage, contributing to a longer-lasting helmet.
  • Cost-effective. ABS plastic provides a protective shell at a lower cost, making it an attractive option for budget-conscious consumers.

Cons of ABS plastic shells

  • Heavier than polycarbonate. The increased weight of ABS plastic can make helmets less comfortable for long rides, especially when compared to lighter alternatives like polycarbonate.
  • Less ventilation. ABS helmets often have fewer vents, decreasing airflow and reducing comfort during warmer rides.
Examples : Bell Sanction, Abus Hyban 2.0

EPS vs EPP vs Koroyd liners

The helmet liner is crucial in providing impact protection during a crash. It is designed to absorb and distribute impact forces, reducing the risk of head injuries. 

Various materials are used for helmet liners, each with advantages and disadvantages.

CharacteristicExpanded Polystyrene (EPS)Expanded Polypropylene (EPP)Koroyd
Impact ResistanceHigh, crushes to absorb impact but doesn’t recover its shapeHigh, crushes to absorb impact but recovers shape, offering multiple-impact protectionHigh, with a unique structure designed to absorb and convert more energy from an impact
VentilationGood, can be molded to include ventsGood, can be molded to include ventsSuperior, the open-cell structure allows for excellent airflow
DurabilityGood, but deteriorates after an impact and needs to be replacedExcellent, retains shape and effectiveness after impactsGood, but should be replaced after a significant impact
Environmental ImpactNot easily recyclable, can take a long time to decomposeRecyclable and reusableKoroyd materials are recyclable and claim to be carbon neutral
PriceAffordable, widely used in helmet constructionMore expensive due to its reusable naturePremium, due to its unique structure and performance characteristics
Comparison between liner materials used in bike helmets

Here is a more detailed explanation of the common liner materials.

Expanded Polystyrene (EPS)

Expanded Polystyrene (EPS) is the most widely used liner material for bike helmets. It is a rigid foam made from small polystyrene beads that are expanded and molded together. Lightweight and effective at absorbing impact energy, EPS foam is suitable for a wide range of helmet designs.

During an impact, the foam compresses, dissipating the energy and reducing the force transmitted to the rider’s head. However, EPS foam is generally designed for one-time use, as it does not fully recover after compression. This means helmets with EPS liners should be replaced after a significant impact.

Pros of EPS liners

  • Lightweight. EPS foam is lightweight, contributing to helmet comfort and reducing strain on the rider’s neck and shoulders.
  • Effective at absorbing impact energy. The foam’s ability to compress and dissipate energy reduces the force transmitted to the rider’s head during an impact.
  • Cost-effective. EPS liners are affordable, making them popular for a wide range of helmet designs.

Cons of EPS liners

  • Designed for one-time use. Since EPS foam does not fully recover after compression, helmets with EPS liners must be replaced after a significant impact to ensure continued safety and protection.
  • Limited impact protection for multiple smaller impacts. While highly effective for single impacts, the one-time use nature of EPS foam may provide less protection in situations involving multiple smaller impacts over time.
Examples : Lazer Z1 MIPS, Giro Aries Spherical, POC Ventral Air SPIN

Expanded Polypropylene (EPP)

Expanded Polypropylene (EPP) is a closed-cell foam with greater resilience than EPS foam.

EPP can withstand multiple impacts without significant degradation in performance by having similar energy-absorbing properties to EPS liners. This makes it an attractive choice for helmets designed for activities with a higher risk of repeated impacts, such as BMX or aggressive mountain biking.

EPP foam is more expensive than EPS foam and may not be as widely available in helmet designs. However, its multi-impact performance can make it a more suitable choice for certain riders and disciplines.

Pros of EPP liners

  • Multi-impact performance. EPP foam can handle multiple impacts without significant degradation in performance, providing ongoing protection during activities with a higher risk of repeated impacts.
  • Resilient and durable. EPP foam is more durable than EPS foam, potentially extending the life of a helmet.

Cons of EPP liners

  • More expensive than EPS foam due to its reusable nature.
  • Less common in helmet designs. EPP foam is not as widely used, which may limit the options for riders seeking this type of liner.
Examples : POC Otocon


Koroyd is a relatively new material used in some helmet liners, consisting of small, welded tubes that create a honeycomb-like structure. This unique design allows for impressive energy absorption and increased airflow compared to traditional foam liners.

When an impact occurs, the Koroyd tubes crumple, absorbing the energy and reducing the force transmitted to the head. Additionally, the open structure of Koroyd promotes ventilation, making it an attractive choice for riders seeking protection and comfort.

Some helmets use Koroyd in combination with EPS or EPP foam, providing a hybrid liner that benefits from the properties of both materials.

Pros of Koroyd liners

  • Effective at absorbing impact energy. The unique honeycomb-like structure of Koroyd effectively absorbs impact energy, providing increased protection during a crash.
  • Improved ventilation and airflow. The open structure of Koroyd allows for better ventilation and airflow, keeping riders cool and comfortable during their rides.

Cons of Koroyd liners

  • Limited availability in helmet designs. Koroyd is still relatively new and not as widely used in helmet designs, which may limit the options for riders seeking this type of liner.
  • More expensive than traditional foam liners.
Examples : Smith Network MIPS, Endura MT500 MIPS

Learn more about bike helmets

Foam vs gel padding

Helmet padding serves multiple purposes, including enhancing comfort, providing a secure fit, and wicking away sweat. Various materials are used for padding in bike helmets, each with advantages and disadvantages. 

Here’s a comparison table focusing on foam, gel, and moisture-wicking fabrics used in bike helmets.

CharacteristicFoam paddingGel padding
ComfortGood, offers cushioning but can absorb sweat and become uncomfortableExcellent, molds to the head for a customized fit, doesn’t absorb sweat
DurabilityGood, but can degrade over time, especially with sweat absorptionExcellent, resistant to sweat and maintains shape over time
MaintenanceNeeds regular cleaning due to sweat absorptionEasy to clean, doesn’t absorb sweat
WeightLightweight, doesn’t add much to helmet weightHeavier than foam, can add weight to the helmet
Heat ManagementPoor, can retain heatGood, doesn’t absorb heat
PriceAffordable, commonly used in helmetsMore expensive due to its superior comfort and durability
Comparison between padding materials used in bike helmets

Here is a more detailed explanation of common padding materials.

Foam padding

Foam padding is commonly used in bike helmets because it is lightweight and cost-effective. It cushions the rider’s head and the helmet’s liner, improving comfort and ensuring a snug fit. Foam padding can be made from various materials, such as polyurethane or EVA (ethylene-vinyl acetate) foam.

Pros of foam padding

  • Lightweight. Foam padding is light, which helps maintain the overall comfort and wearability of the helmet.
  • Affordable. Using foam padding in helmet designs is cost-effective, making it accessible for a wide range of budgets.
  • Provides cushioning for added comfort. Foam padding enhances comfort by cushioning between the rider’s head and the helmet’s liner.

Cons of foam padding

  • Absorbs sweat, leading to reduced comfort and hygiene over time.
  • Average durability. May compress and lose its cushioning properties with extended use.
Examples : Giro Synthe MIPS, POC Ventral Air SPIN, Specialized S-Works Prevail II

Gel padding

Gel padding is a more advanced option, offering improved comfort and cushioning than traditional foam padding.

It conforms to the shape of the rider’s head, distributing pressure evenly and reducing the risk of pressure points or hot spots. Some gel padding materials also have temperature-regulating properties, helping to keep the rider’s head cool during hot rides.

Pros of gel padding

  • Conforms to the rider’s head for a custom fit. Gel padding adjusts to the shape of the rider’s head, providing a personalized fit and increased comfort.
  • Offers superior cushioning and comfort. Gel padding delivers improved cushioning compared to foam padding, enhancing the overall comfort of the helmet.
  • Good heat management. Some gel padding materials have temperature-regulating properties, which can help maintain a comfortable head temperature during hot rides.

Cons of gel padding

  • Heavier than foam padding. Can be less comfortable during longer rides.
  • More expensive than foam padding due to its superior comfort and durability
Examples : Lazer G1 MIPS, MET Trenta 3K, Scott Cadence Plus

Retention system materials

Retention systems play a critical role in ensuring that a bike helmet stays securely in place during a ride and in the event of a crash. These adjustable systems provide a snug, comfortable fit while allowing riders to customize the helmet’s tightness to suit their head shape and size. 

Here’s a detailed explanation of common retention system types and their features.

Dial Adjust System

Dial adjust systems, also known as micro-adjust systems, are among modern bike helmets’ most popular retention systems. They feature a dial at the back of the helmet, which can be turned to tighten or loosen the fit.

These systems provide a high level of adjustability and precision, allowing you to fine-tune your helmet fit easily.

Pros of dial adjust systems

  • Precise and easy-to-use adjustments. Dial adjust systems allow for accurate and user-friendly adjustments, ensuring a secure and comfortable fit.
  • Evenly distributes pressure for a comfortable fit. By tightening or loosening the helmet evenly, these systems help to prevent pressure points and ensure a snug, comfortable fit.
  • Often compatible with one-handed adjustments while riding. Many dial adjust systems can be operated with one hand, allowing riders to adjust without stopping.

Cons of dial adjust systems

  • May add weight and complexity to the helmet. Can increase a helmet’s overall weight and complexity compared to simpler retention systems.
  • Can be more expensive than other retention systems due to their enhanced adjustability and convenience.
Alex Lee at Mr.Mamil

Alex Lee is the founder and editor-at-large of Mr. Mamil. Coming from a professional engineering background, he breaks down technical cycling nuances into an easy-to-understand and digestible format here.

He has been riding road bikes actively for the past 12 years and started racing competitively in the senior category during the summer recently.