How We Develop Our Brake Rotor Guards

In the previous blog we explained why brake rotor guards exist and why mountain biking has started to take them seriously. This follow-up looks at the other side of the equation: how we actually develop one so it works properly in real riding and racing conditions.

A rotor guard is a simple idea. The challenge isn’t the concept itself, it’s managing all the constraints that come with fitting a part into a tight, hostile area of the bike and making sure it behaves consistently over time. Clearances are small, tolerances stack up quickly, and the part has to survive impacts, contamination, temperature swings and repeated handling. Getting it wrong is easy. Getting it right requires a structured process and constant iteration.

 

Starting With Real Geometry, Not Assumptions

One of the most common mistakes in component design is working from nominal drawing dimensions or from rough measurements taken directly from a complex assembly. On parts like forks and brake systems, this approach quickly introduces compounding errors. Forks are cast, machined and finished components with tolerances that vary more than most people expect. Add wheel flex, rotor construction and positioning, brake alignment and calliper variation into the mix, and small assumptions can escalate into significant fitment issues.

To avoid this, we start by capturing the actual geometry of the fork and brake assembly using 3D scanning. This produces a point-cloud representation of what exists on the real bike, not an idealised version of it. We scan multiple assemblies using different calliper brands, rotors and hubs to understand the full range of dimensional constraints created by different setups, rather than designing around a single configuration.

Raw scan data is heavy and unrefined. A single scan contains millions of points, including noise, reflections and irrelevant surfaces. The first step is processing that data into a clean, manageable mesh that preserves accuracy without overwhelming the CAD environment. The mesh is never turned into a solid model. It remains reference geometry that defines spatial constraints and real-world clearances.

Using Scan Data Properly in CAD

A common misconception around 3D scanning is that once the scan exists, you can simply copy it or design directly on top of it. In reality, scan data is not something you design with. It’s something you design against.

Once the scan is correctly positioned in CAD, it becomes a spatial reference. Key areas such as fork legs, calliper position, rotor position and clearance envelopes are identified. Sketches and surfaces are then built relative to that reference data, not arbitrarily in space.

This approach allows the part to follow the natural geometry of the fork rather than fighting it. Clearances are intentional rather than guessed. It also allows the guard to sit snugly around the brake assembly, which is important not just for fit but also for reducing unnecessary air gaps around the calliper. That has a direct effect on consistency and heat behaviour.

Surface Design and Organic Geometry

Rotor guards sit in a visually exposed area and interface with curved fork legs and moving components. They are not blocky parts, and treating them as such usually leads to awkward shapes, poor stress distribution, and designs that look out of place on the bike.

For this reason, the design is driven primarily by surface modelling rather than simple solid bodies. Surface-based design allows controlled transitions, smooth curvature and continuous geometry that better reflects the organic shapes of modern forks. It also makes it possible to manage wall thickness and stiffness more precisely, which is critical for a part that has to be light, stiff and impact resistant at the same time.

Hard edges where they are not required tend to concentrate stress, trap debris and create visual noise. Controlled surface transitions behave better mechanically and integrate more naturally with the bike and fork design.

At this stage, the part is also designed around how it will actually be used. Fast wheel changes, easy access to bolts, no unnecessary steps and no interference with brake servicing matter just as much in a World Cup pit as they do in a home workshop. A part that adds time or complexity will not last long in a racing environment.

Designing for Additive Manufacturing

A part designed for machining behaves very differently from one designed for additive manufacturing. With 3D printing, material characteristics, fibre direction, layer orientation and wall structure directly affect stiffness, impact resistance and durability.

During the design phase we consider how the part will be oriented during printing, where load paths exist and how stresses are transferred through the structure. Features that look acceptable on screen can fail quickly if they are not aligned with how the printed material actually carries load.

Support strategy is also considered early. Supports affect surface quality, print time and material waste. A design that relies heavily on supports or requires extensive post-processing is usually a sign that the geometry should be simplified earlier rather than corrected later.

Materials and Prototyping Strategy

Throughout development we have tested a wide range of materials, including multiple engineering-grade carbon-fibre-reinforced filaments. Each material behaves differently in terms of stiffness, impact resistance, surface finish and print stability. The final guards are produced using a high-grade engineering material, but the exact formulation is not the important part here.

Early prototypes are often printed in lower-cost materials such as PLA to validate overall shape, fitment and clearance. This stage is useful, but limited. These materials behave very differently both during printing and in use, so they are not a reliable indicator of final performance.

As the design progresses, prototypes move into the same class of engineering-grade material used for production. This is where real behaviour under load, resistance to impacts and long-term durability start to matter. It’s also where printing parameters become critical.

 

Printing Parameters Matter More Than People Think

Printing a functional part is not just a case of pressing “print”.

Engineering-grade carbon-reinforced materials require careful preparation, controlled storage and consistent handling. Printing conditions are narrow, and small deviations in temperature, speed, flow or cooling can cause failures. These materials are also abrasive, which accelerates wear on printer components and adds another layer of maintenance to the process.

Each guard takes around twelve hours to print. A failure early in the process is inconvenient but manageable. A failure late in the print means wasted material, wasted time and starting again. This reality is part of working with demanding materials and reinforces why consistency matters, both to achieve repeatable performance and to minimise material waste.

The goal is repeatability. Every single part needs to behave the same way, not just the one that came out perfect.

Testing: Controlled and Real World

Before anything goes on a bike, prototypes are tested in controlled ways. Loads are applied along defined axes to understand how the structure reacts, where it deforms and where it fails. These tests are used to confirm assumptions and identify weak points early so the design or manufacturing process can be refined.

Real performance validation happens through riding. Mud, water, grit, low temperatures and repeated braking expose issues that no bench test can fully replicate. Long runs, cold race starts and poor conditions are where problems show up and where the design is genuinely stressed.

Development has included direct testing and rider feedback within the World Cup environment with Santa Cruz Syndicate, including some of the most demanding race conditions. Events like Les Gets in 2025, run in heavy rain and muddy conditions, proved to be a decisive test. The feedback from riders was consistently positive, particularly in terms of braking consistency and reliability when conditions were at their worst.

Why This Process Matters

None of this is glamorous, and it doesn’t need to be. The point of the process is not to impress, it’s to remove problems quietly and consistently.

The rotor guards available today are the result of balancing geometry, material behaviour, manufacturing constraints and real-world use without letting any single factor dominate the design. When it works properly, it doesn’t draw attention to itself. It just does its job, run after run.

If you’ve read our first blog on why rotor guards exist, this one should make it clear why execution matters just as much as the idea. And if you want to see how this approach translates into a finished component, the rotor guard developed through this process is available on the products page.