We would like to introduce you to a very special duo: the Porsche 911 GT3 RS with the Weissach Package, and the custom Harley-Davidson Softail Breakout built to match it: the Thunderbike GP-Weissach.
Together with our customer Stefan, we created a project that bridges the gap between high-performance automotive engineering and handcrafted custom motorcycle design. This is not our first collaboration with him. Nearly ten years ago, Stefan inspired one of our most iconic builds, the Lamborghini Aventador–themed Thunderbike OUTERLIMIT. Now, the story continues with a new interpretation of power, precision and style.
The inspiration for the GP-Weissach project comes directly from Stefan’s Porsche 911 GT3 RS (992.1), a machine that represents the ultimate track-focused driving experience. Its 4.0-liter naturally aspirated engine delivers 525 hp, accelerating the 1450 kg car from 0 to 100 km/h in just 3.2 seconds. The Weissach Package further enhances performance by reducing weight by around 15 kilograms through targeted lightweight construction.
Visible high-gloss carbon components such as the front hood, roof, exterior mirrors and wing elements emphasize the motorsport character. Inside, the combination of Race-Tex upholstery, red contrast stitching, magnesium shift paddles and carbon fiber surfaces reflects a pure racing atmosphere. Even the magnesium wheels finished in Pyrored inspired the key color accents of our motorcycle.
For the bike, we selected the Harley-Davidson Breakout FXBRS with Milwaukee-Eight engine as the foundation. This model offers the ideal frame geometry to integrate our GP rear conversion and the substantial 9×21-inch rear wheel. The cockpit retains the original digital speedometer but is now seamlessly integrated into a custom-milled triple clamp. The goal was not to copy the Porsche, but to interpret its attitude. Colors, proportions, finishes and materials were chosen to translate the GT3 RS design language into a new aesthetic expression on two wheels.
The GP-Weissach incorporates the latest developments from our high-end GP component line. It features aerodynamically optimized triple clamps, redesigned handlebar mounts with Rebuffini RR90 controls, and a new GP front mask, all contributing to a dynamic and athletic stance. The open primary drive adds mechanical transparency and highlights the powertrain.
The single-sided swingarm, milled from a solid block of aluminum, allows an unobstructed view of the wheel. An air suspension system at the front and a hydraulically adjustable rear setup lower the bike when parked, giving it a dramatic, grounded presence.
A defining aspect of the design is the use of Pyrored accents, directly referencing the Porsche’s wheel color. The wheels of the GP-Weissach are milled from a single piece, then selectively machined after anodizing to create depth, sharp edges and visual motion. Their five-spoke Y-design appears lightweight and technical, perfectly matching the sporty and high-end character of the build. The exposed 21-inch rear wheel, combined with the perimeter brake system, serves as both a functional and visual centerpiece that underscores the precision and craftsmanship of the motorcycle.
At the end of the project, Stefan summed up his feelings in one sentence: “My goal was 100%. You delivered 110%.” For us, that is the greatest recognition. The GP-Weissach is more than a custom motorcycle. It is the translation of supercar performance philosophy into hand-built motorcycle culture. A Porsche created for the racetrack, and a Harley reinvented to share its spirit. Two machines, one shared heartbeat of motorsport passion.
