From Concept to Market Readiness
The Development of the ROTWILD R.EXC
Every innovation begins with a spark—a thought that ignites, unfolds, and sets the development process in motion. It’s the drive to surpass the status quo: faster, more precise, more comfortable. This is how the vision for a new bicycle model emerges, fueled by inspiration and the ambition to push boundaries. Yet, countless hours of intensive development, testing, and optimization lie between the initial concept and the first test ride.
In this series, we aim to take you behind the scenes and reveal what goes into developing an E-mountain bike. From the initial idea to technical conception, prototype testing, and fine-tuning, we’ll show you who is involved, the necessary processes, and the passion that goes into every new ROTWILD bike. Representing the project, we will hear from three key players in the process: developer Lutz Scheffer, test rider Claudio Caluori, and team rider Torben Drach. They all have a lot to share—from the first spark of inspiration to the market readiness of the ROTWILD R.EXC.
A Revolution in Race-Enduro – The ROTWILD R.EXC
Developing an Enduro E-mountain bike is no small feat. These bikes are designed to combine seemingly contradictory qualities: climbing agility and downhill control. Achieving this balance requires meticulous attention to every detail—perfect geometry, a powerful drive system, and a suspension that performs uphill without sagging, while delivering sensitivity and maximum control downhill. A single misstep can tip the entire concept off balance. For over 25 years, ROTWILD’s history has been marked by a relentless pursuit of the ultimate bike—breaking new ground and daring to innovate. This journey led to the creation of a truly exceptional bike: the new Race-Enduro ROTWILD R.EXC. The development of this high-performance machine was led by none other than Lutz Scheffer, a visionary industrial designer and long-standing member of ROTWILD’s engineering team. In close collaboration with company founder Peter Schlitt, he shaped the idea of a bike that perfectly embodies the spirit of the brand.
The development of a new product is an intensive, multifaceted process that combines creative vision with precise teamwork. From the initial idea to prototype development, practical testing, and achieving final market readiness, each phase demands seamless collaboration between developers and athletes. This close partnership ensures that the product meets not just theoretical requirements but also real-world racing conditions.
The Challenge: A Race-Enduro Without Weaknesses
The project began with a blank slate—starting entirely from scratch without predefined parameters. It was clear from the outset that a bike like the R.EXC could not be achieved by modifying an existing model. Something completely new had to be created. “An E-Enduro that excels both uphill and downhill was our goal—and that is the ultimate discipline,” explains Lutz Scheffer, describing the challenge behind the project.
Lutz, an avid mountain biker himself, speaks from experience. He spends nearly every day in alpine terrain, gathering ideas for new projects on his rides. With the R.EXC, the objective was clear: to develop the best E-Enduro on the market—uncompromising, innovative, and exceptionally powerful, all while continuing the racing technology legacy of ROTWILD.
The question was straightforward, but the answer was far from trivial: What defines the perfect E-Race-Enduro? A climbing machine that’s fast and technically adept uphill, even on root carpets and rocky ascents, with zero compromises. A bike that pushes the limits of what’s possible downhill—precise, agile, and intuitive, almost as if it anticipates the rider’s line. It must adapt to varying conditions and riding styles, while remaining robust and responsive without feeling sluggish. “What you lose uphill in a race, you can’t make up downhill,” Scheffer emphasizes. “The bike must perform in every situation. There’s no second chance.”
The Beginning: Everything Is Possible
A wish list of ambitious goals led to a pivotal decision: it wouldn’t suffice to alter existing concepts if the aim was to set new benchmarks. A ground-up rethinking was required. “Our approach was to rethink the kinematics entirely,” Scheffer explains. “This led us to a completely novel design: the Mid-High-Pivot system.” This method embodies ROTWILD’s engineering philosophy—to scrutinize the status quo and improve step by step. This foundation is built on years of accumulated expertise and a passion for reimagining concepts.
But before even a single piece of aluminum was milled or a component tested, the design’s cornerstones had to be defined. On the computer, a bike like no other emerged—an unconventional design for ROTWILD. Using 3D modeling and simulations, the first draft was created. This stage involved no assembly or welding, only calculations: How long should the reach be to ensure stability and control? How flat can the seat angle be without compromising uphill performance? How do you balance smoothness and agility? “The possibilities of 3D printing allowed us to make precise adjustments to components and frames, testing them in detail from an early stage,” Scheffer recalls. “Working on this project was demanding, but every decision was made with passion, always aiming to develop a bike that meets our highest standards.”
The Mid-High-Pivot System: A Revolution in Rear Suspension Kinematics
The centerpiece of the R.EXC quickly became evident: the Mid-High-Pivot system, a groundbreaking innovation in rear suspension design. This system moves the main pivot point of the rear triangle to an unconventional, new position.
“The pivot is positioned higher and farther forward than on traditional bikes,” explains Scheffer. “This design offers crucial advantages: the higher anti-squat value keeps the bike more stable within its travel, significantly improving power transfer during pedaling. Anti-squat refers to the resistance of the rear suspension to compress under pedaling forces. The R.EXC’s Mid-High-Pivot system ensures constant anti-squat values throughout the entire travel, delivering maximum efficiency and stability.”
Traditionally, anti-squat is calibrated to 100% at SAG. However, conventional anti-squat kinematics have the significant drawback of varying greatly throughout the travel. At the start of the travel, there is too much anti-squat, while at the end, there is too little. “With this fundamental flaw, we decided to take action,” explains Lutz Scheffer. “The mid-high pivot allows anti-squat to remain consistently high throughout the entire travel. We achieved a constant 120% anti-squat in the 34-45 gear combination across the entire range of motion. This is unique in the world of kinematics. The reason we opted for 120% instead of the traditional 100% anti-squat lies in the demands of modern powerful e-bike motors. When climbing steep inclines, weight shifts significantly to the rear wheel. To prevent the suspension from compressing under such extreme conditions, a robust 120% anti-squat is required to keep the rear suspension stable.” This system delivers exceptional stability on technical trails and steep climbs. The suspension remains active without sagging, ensuring consistent traction.
“By positioning the mid-high pivot further forward, we achieve a longer swingarm with a noticeably smoother, less curved axle path,” Scheffer continues. “The result is controlled and predictable handling, even in demanding terrain.”
The Box Design: Symmetry Meets Stability
Another striking innovation of the R.EXC is the distinctive box design of the swingarm. As a passionate track-day and endurance racing motorcyclist, Lutz Scheffer developed a motorcycle-inspired structure. The monobox design offers exceptional stability, delivering a torsionally stiff and high-performance rear end. The monobox swingarm achieves an optimal balance between necessary torsional flex and lateral stiffness. “Unlike conventional bikes, which have asymmetrical rear ends due to the motor, chainring, and tire, we took an unconventional approach,” Scheffer explains. “We routed the chainstays over the top, enabling us to design a symmetrical and robust swingarm.”
This innovative construction provides multiple significant technical advantages. The symmetrical stiffness ensures precise and consistent cornering response, regardless of direction. This creates an extraordinary riding feel with maximum predictability and control. Furthermore, the monobox design nearly eliminates unwanted flex, significantly increasing frame rigidity.
The monobox swingarm is capable of delivering the desired torsional flex while maintaining high stiffness in all other dimensions. This unique combination of excellent torsional flex and high bending stiffness translates directly into improved ride dynamics, offering the rider more precise power transfer and stable handling in all riding conditions. With the box design, we achieve high chain tension stiffness, effectively preventing unwanted “fishtailing,” or rear-wheel steering. Simultaneously, the box swingarm allows for harmonious torsional flex, symmetrical in both left and right lean angles.
This torsional flex, acting like an additional damper, is finely tuned to provide optimal grip levels on low-traction surfaces.
ROTWILD R.EXC
At a glance
- Frame: Full carbon made from high modulus carbon fibers, handmade
- Fork: 170 mm travel / Fox Float 38 Factory Kashima
- Shock: adjustable travel 160/150/145 mm / Fox Float X 2-Pos Adjust EVOL LV Factory Kashima
- Front tire diameter: max. 29x2.6
- Rear tire diameter: max. 27,5x2.6
- Permissible total weight: 130 kg
- Motor: Shimano EP801 / up to 85 Nm torque
- Battery: IPU Carbon / effective 820 watt hours / 4.5 A charger
- Color: Red Transparent
- Sizes: S / M / L / XL
- Weight: 22,0 kg
“What you lose uphill in a race, you can’t make up downhill,”
“The bike must perform in every situation. There’s no second chance.”
Lutz Scheffer, Advanced Design Developer
