MIPS vs Spherical vs 6D ODS: which rotational system is safest?

Introduction: Why Rotational Impacts Matter

When a rider crashes, the head rarely hits the ground in a perfectly straight line. Most real-world impacts happen at an angle, causing the head to twist suddenly as it slows down. This twisting motion creates rotational acceleration, which places significant strain on the brain as it moves and deforms inside the skull. Research has shown that this type of motion is strongly linked to concussions and other diffuse brain injuries, even in crashes that do not feel especially violent.

For decades, helmet safety focused almost entirely on linear impact protection, measuring how well a helmet could absorb a straight-on blow. Standards and certifications, such as DOT, ECE, and CPSC, were built around this concept, tracking how much force traveled directly through the helmet to the head. While this approach reduced catastrophic injuries like skull fractures, it did not fully address the rotational forces common in most real-world crashes. As understanding of brain biomechanics improved, helmet design began to evolve to manage both straight-line impacts and angled ones.

This shift led to the rise of rotational protection systems like MIPS-equipped helmets, Spherical MIPS helmets, and 6D ODS helmets. Each takes a different engineering approach to the same goal: reducing the rotational forces transmitted to the brain during an impact. The key question is not whether rotational protection matters, but whether one system is objectively safer than the others. As evidence shows, that answer is more complex than a single name or logo on the helmet shell.

What Do We Mean by “Safest” in Helmet Design?

When riders ask which helmet is the safest, the word “safest” can mean very different things depending on context. At a minimum, a helmet must meet certification standards such as CPSC, EN, DOT, or ECE. These tests confirm that a helmet can manage severe impacts without catastrophic failure, but passing a certification does not mean all certified helmets offer the same level of protection in every crash scenario.

Most safety standards focus heavily on linear impacts, where the helmet is dropped straight down onto a hard surface at a set speed. These tests are effective at reducing life-threatening head injuries, but they only represent a narrow slice of real-world crashes. Angled impacts, lower-speed falls, and complex multi-directional forces are either simplified or not fully represented in current certification protocols. As a result, two helmets that both pass the same standard can perform very differently when rotational forces are involved.

Rotational protection systems like MIPS helmets, Spherical MIPS helmets, and 6D ODS helmets exist because of these gaps. They are designed to address crash dynamics that baseline certifications do not directly measure, particularly the twisting motion of the head during oblique impacts. Importantly, these systems do not replace certification requirements. They are layered on top of them, adding another level of protection rather than redefining the minimum bar for safety.

With that context in mind, this guide does not attempt to crown a single helmet technology as universally safest. Instead, it examines how different rotational systems work, what independent testing can and cannot tell us, and why real-world helmet safety depends on the complete design, fit and sizing, and intended use rather than one feature in isolation.

How Rotational Helmet Systems Work

In a real-world crash, the head usually strikes the ground or an object at an angle rather than straight on. This type of hit is known as an oblique impact. Instead of stopping abruptly, the helmet catches and grips the surface for a brief moment, causing the head to rotate as it decelerates. That sudden rotation creates angular acceleration, which can place damaging shear forces on brain tissue.

Rotational helmet systems are designed to reduce how much of that twisting motion is transferred to the head. They do this by allowing controlled movement within the helmet during an impact. Rather than the helmet and head stopping and rotating as one rigid unit, part of the helmet is allowed to shift, rotate, or deform in a managed way. This movement helps lower the peak rotational acceleration that reaches the brain, which is believed to reduce the risk of concussion and other traumatic brain injuries.

While the underlying goal is the same, the way each system achieves it can vary significantly. Some rely on low-friction slip layers, like those found in MIPS helmets, others use dual EPS liners as seen in Spherical MIPS helmets, and some incorporate elastomer-based suspension elements, such as in 6D ODS helmets. What matters most is how well the entire helmet works as a system. Shell shape, foam density, liner thickness, coverage area, and proper fit all influence how rotational forces are managed. A well-designed helmet with a modest rotational system can outperform a poorly designed helmet with more complex technology, which is why overall helmet design is just as critical as the rotational system it uses.

MIPS (Classic Slip-Liner System

What It Is

MIPS, which stands for Multi-directional Impact Protection System, is one of the earliest and most widely adopted approaches to rotational impact management. The classic MIPS design uses a thin, low-friction plastic liner mounted inside the helmet, positioned between the comfort padding and the EPS foam. This liner is anchored in a way that allows it to move slightly when the helmet experiences an angled impact. You can find MIPS technology in Bell MX9 MIPS helmets and Bell Moto‑10 MIPS helmets, among many others.

What It’s Designed to Reduce

The purpose of this slip-liner is to reduce rotational acceleration transmitted to the head during oblique impacts. When the helmet contacts the ground at an angle, the low-friction layer allows the helmet shell and outer foam to rotate slightly relative to the head. By permitting this controlled movement, MIPS aims to lower the peak twisting forces that reach the brain, helping to reduce the risk of concussion and other traumatic brain injuries.

Where It’s Used

One of MIPS’s defining characteristics is its broad adoption. The system is licensed to a wide range of manufacturers and appears in helmets across many categories and price points. Road, mountain, commuter, and moto helmets commonly include classic MIPS, making it one of the most familiar rotational protection labels on the market.

Strengths and Limitations

The biggest advantage of MIPS is scale. Because it is used in so many helmets, it has been incorporated into a large number of models that have undergone independent laboratory testing. This makes it easier to find MIPS-equipped helmets that score well in third-party rankings. At the same time, MIPS does not guarantee top performance on its own. The system’s effectiveness depends heavily on the overall helmet design, including shell geometry, foam tuning, coverage, and proper fit. A well-designed non-MIPS helmet can outperform a poorly executed MIPS helmet, which highlights that MIPS is a component, not a complete safety solution.

Spherical MIPS (Ball-and-Socket Design)

How Spherical Differs from Classic MIPS

Spherical MIPS takes a different approach from the traditional slip-liner design. Instead of adding a separate low-friction layer, it uses two distinct EPS foam liners that fit together in a ball-and-socket arrangement. The rotational movement happens between these two foam layers, with MIPS technology integrated into the structure itself rather than added as a separate sheet inside the helmet. You can explore this technology in Bell Moto‑10 Spherical helmets.

Intended Benefits

By building rotational movement into the foam layers, Spherical MIPS is designed to manage angular acceleration while improving comfort and ventilation. Eliminating the plastic slip liner can reduce pressure points against the head and allow for larger ventilation channels. The goal is to provide rotational protection without the feeling that something is floating or shifting against the scalp during normal riding.

Availability and Design Dependence

Spherical MIPS is not widely licensed in the same way as classic MIPS. It is found almost exclusively in higher-end helmets from Bell and Giro, where those brands can design the entire helmet around the dual-liner concept. Because of this, performance varies from model to model and depends heavily on how the helmet shell, foam densities, and coverage are tuned around the Spherical system.

Strengths and Limitations

The main strength of Spherical MIPS is its integrated design. Rotational management, comfort, and ventilation are all addressed within the helmet’s core structure rather than added afterward. The primary limitation is availability. Because the system is limited to a relatively small number of premium models, there is less variety and less independent testing data compared with classic MIPS. As with any system, the final level of protection still depends on the complete helmet design rather than the technology name alone.

6D ODS (Omni-Directional Suspension)

Core Design Concept

6D’s Omni-Directional Suspension, often referred to as ODS, is built around the idea that a helmet should behave more like a suspension system than a single rigid structure. Instead of relying on a single block of EPS foam, 6D helmets use two separate EPS liners. These liners are connected by a network of small elastomer dampers shaped like hourglasses, which sit between the inner and outer liners. You can find this system in 6D Men’s Dirt Bike Helmets.

Degrees of Freedom Explained

The elastomer dampers allow the two liners to move relative to each other in multiple directions. This includes both rotational movement and translational movement, meaning straight-line motion along different axes. Together, this is often described as six degrees of freedom. The intent is to let the outer shell manage the initial impact while the dampers absorb and control motion before it reaches the head, then gradually return the inner liner to its original position.

Impact Range Focus

6D emphasizes performance across a wide range of impact energies. The ODS system is designed to respond not only to high-speed crashes, but also to lower-speed impacts that may not fully engage traditional foam-only designs. By allowing controlled movement and damping over a longer time window, the system aims to reduce both peak linear forces and peak rotational acceleration across different crash scenarios.

Strengths and Limitations

The strength of 6D ODS lies in its technical ambition. It is one of the most complex rotational and linear energy management systems used in helmets, with a clear focus on managing multiple types of motion. The main limitation is the scope of independent evidence. ODS appears in a relatively small number of helmet models, and there is less third-party testing data available compared with more widely adopted systems like MIPS helmets. As a result, real-world performance must be evaluated helmet by helmet rather than assumed based on the system alone.

Independent Testing and What It Actually Measures

Certification Testing vs Advanced Lab Testing

Helmet certification tests are designed to ensure a basic level of protection and to prevent catastrophic failure. Standards such as CPSC, EN, DOT, and ECE focus primarily on high-energy linear impacts. Helmets are dropped vertically onto rigid anvils to measure how much straight-line force is transmitted to a headform. These tests are effective at reducing severe head injuries, but they simplify real-world crashes and largely overlook the complex rotational forces that occur in angled impacts.

Advanced laboratory testing attempts to fill some of these gaps. Instead of only measuring linear acceleration, these tests introduce oblique impacts and record rotational motion as well. This provides a more detailed picture of how a helmet manages the twisting forces that are strongly associated with concussions. Importantly, these tests go beyond pass-or-fail results and allow helmets to be compared against each other on a performance scale.

Virginia Tech STAR Ratings Explained

One of the most widely referenced independent testing programs is Virginia Tech’s STAR helmet rating system. In these tests, helmets are dropped onto angled, abrasive surfaces designed to create both linear and rotational acceleration. Sensors inside the headform measure how the helmet performs in multiple impact locations and at different speeds.

The data from these impacts is then converted into a concussion risk estimate, summarized as a STAR value. Lower STAR values indicate a lower estimated risk of concussion. Helmets are grouped into star ratings that make it easier for consumers to compare models within the same category, such as mountain biking, road cycling, or motocross helmets.

What the Rankings Show in Practice

When looking at independent rankings, it becomes clear that high performance is spread across multiple technologies. Many of the top-rated helmets use classic MIPS helmets, which reflects how widely the system is adopted and how many MIPS-equipped helmets are available for testing. Some Spherical MIPS helmets from Bell and Giro also appear near the top of the rankings, showing that the integrated dual-liner approach can perform very well when paired with strong overall helmet design.

6D ODS helmets appear less frequently in these rankings, largely because there are fewer models available and fewer categories in which they are tested. Some 6D helmets score very well, while others perform more moderately, which reinforces an important point: independent rankings evaluate complete helmets, not individual rotational systems in isolation. The technology label alone does not determine the outcome; the full design of the helmet does.

Marketing Claims vs Independent Evidence

Helmet manufacturers often conduct their own tests to evaluate how their rotational systems perform. These internal results can highlight strengths and improvements over previous models, but they are not standardized and are typically conducted under controlled conditions that may not reflect real-world crashes. Third-party, independent testing provides a more objective assessment because it uses consistent methods across multiple brands and models.

It is common to see marketing claims suggesting that one system, such as 6D ODS helmets, surpasses others in protection. Similar claims are sometimes made for classic MIPS helmets or Spherical MIPS helmets. While these statements can be supported by selective internal testing, they do not always align with independent results. Consumers should understand that marketing materials are designed to promote the product and may not represent comprehensive scientific evidence.

There are no large-scale, head-to-head comparisons that isolate a single rotational system across multiple helmet models under standardized conditions. Every independent test evaluates complete helmets, which means performance is influenced by the shell, foam, fit, and coverage in addition to the rotational technology. As a result, it is impossible to declare a single system universally superior based solely on available evidence.

Side-by-Side Comparison: Rotational Systems at a Glance

So… Which Rotational System Is Actually Safest?

No single rotational system can be declared universally safest. Independent testing evaluates complete helmets rather than isolated technologies, which means the performance of a helmet depends on the combination of rotational system, shell design, foam density, coverage, and fit. A helmet with a modest rotational system can outperform a helmet with a more complex system if the overall design is superior.

Current evidence shows that helmets using classic MIPS helmets and Spherical MIPS helmets often perform very well in independent STAR ratings, largely because these systems are widely adopted and paired with well-developed helmet designs. 6D ODS helmets are technically ambitious and perform strongly in some helmets, but fewer models have been tested independently, which limits the ability to make broad claims. What evidence does not show is that one system automatically provides the highest protection in all crash scenarios.

Helmet design, proper fit, and validated testing results remain the most important factors for safety. A helmet that fits snugly, covers key areas of the head, and scores well in independent testing will generally provide more reliable protection than simply choosing a helmet based on the rotational system it uses.

What Riders Should Prioritize When Choosing a Helmet

Independent Test Results

The first factor to consider is independent test performance. Programs like Virginia Tech’s STAR ratings provide objective data on how helmets handle both linear and rotational forces. Choosing a helmet that scores well in these tests ensures it has been evaluated under consistent conditions and can give a more reliable indication of protection. Riders should consult up-to-date ratings for their specific category, such as road, mountain, or motorcycle helmets.

Fit, Stability, and Coverage

Even the most advanced rotational system cannot compensate for a helmet that does not fit properly. A helmet should sit snugly on the head without shifting during movement. Poor fit reduces the effectiveness of any protective technology and increases the risk of injury. Coverage is also critical, particularly around the temples and back of the head. A well-designed helmet that stays stable and covers vulnerable areas will always provide better protection than one that fits poorly. Riders can consult helmet sizing guides to ensure proper fit.

Intended Use and Riding Category

Different riding styles and conditions place different demands on a helmet. Higher-risk activities such as downhill mountain biking, motocross, or high-speed motorcycling may benefit from helmets that meet more rigorous standards and include modern rotational systems like MIPS helmets, Spherical MIPS helmets, or 6D ODS helmets. For commuting, gravel riding, or road cycling, a lighter, well-ventilated helmet with solid test ratings may be the better choice. Matching the helmet to the intended use ensures the best combination of protection, comfort, and practicality.

Final Takeaway

Rotational protection systems play an important role in modern helmet safety. They help reduce the twisting forces that can cause concussions and other brain injuries, adding a layer of protection beyond what standard certification tests measure.

There is no single rotational system that can be called the safest for all helmets and all crash scenarios. Performance depends on the full helmet design, fit, and independent test results rather than the technology label alone.

The safest helmet for any rider is one that fits properly, provides good coverage, and scores highly in independent laboratory testing for their specific use case. Choosing a top-rated helmet that matches the rider’s intended activity ensures the best combination of protection, comfort, and reliability.