This article was produced in collaboration with Wilier and was first published in Rouleur Issue 140
When Wilier Triestina asked themselves the question – how can we raise the performance bar even higher? – they knew that simply chasing numbers in the wind tunnel wouldn’t be enough. Their goal was to combine extreme aerodynamics with light weight, responsiveness, and ride quality. They wanted scientifically validated performance, measurable advantages and authentic feelings on the road – and over a five-year development period they found them.
For the new Filante SLR ID2, Wilier’s engineers worked hand in hand with the Groupama-FDJ team, analysing every detail of the bike, the riding, and the environment in which it would perform. From the NACA airfoils (the shapes used in aeronautics) of the fork and the new Aerokit main triangle to the redesigned seatpost, the perfect integration of the Shimano Di2 battery and the geometries developed alongside WorldTour pros, the resulting bike is the ultimate expression of Italian craftsmanship, precision engineering, WorldTour experience, and cutting-edge aerodynamics. Wilier’s Innovation Lab started by using advanced CFD (computational fluid dynamics) to translate the design brief into a digital 3D model consisting of a frame, fork and handlebar. Next, the model was split virtually into thousands of small cells to create a mesh in order for airflow around the bike to be analysed, remodelled and optimised.
The team began with the leading edge of the bike – the surfaces that interact first with the airflow. Fork, head tube, down tube and seatpost were tuned to keep laminar flow attached for longer, reducing turbulence and gaining advantages step by digital step.
For the fork Wilier analysed several NACA airfoil profiles in conjunction with wheel and tyre models, using CFD to simulate multiple wind angles and real-world conditions. The volume of simulation work was three times that used for its previous Supersonica SLR TT bike project.
The result: a fork combining an external NACA-style airfoil leg and a flat inner profile, designed to minimise airflow interference with wheel and tyre and to maximise aerodynamic efficiency. A steeper crown-cone geometry – a learning from the Verticale SLR – gives greater torsional stiffness and improved steering precision. A slim aerodynamic fin on the left leg fairs the brake caliper while the thru axle clamping bushing has been completely encased into the right fork leg – subtle details that blend aesthetics and performance.
Meanwhile, the head tube was refined to allow the air to flow even more smoothly. Cables are routed directly from the handlebar, creating a cleaner silhouette, better aerodynamics and that sense of integrated craftsmanship.
Presiding over it is the new F-Bar ID2 cockpit, developed alongside the Groupama- FDJ riders. Nine moulded titanium prototypes were tested before Wilier’s engineers settled on the final O.E.F. (Optimised Ergonomic Flare) design, which flares 3cm between the high and low positions. This allows greater control in the drops and a more tucked and aerodynamically efficient position on the hoods, with a natural and comfortable grip.
The F-Bar’s integration with the frame is seamless: it introduces new covers and concave spacers that increase contact surface; there’s hidden clamping hardware for the first time on a Wilier product and the convex shape of the handlebar curve reduces the height difference between the handlebar and the top tube – all contribute to aesthetic continuity and aerodynamic performance. And the Filante SLR ID2 remains compatible with other Wilier bars for different setup options.
Perhaps the single most complex area was the down tube – always the most challenging element of aero design. The objective: minimal drag and minimal exposure of water bottles to the airflow.
Wilier chose a dual-section design: a thin upper profile near the head tube with an airfoil shape, with a wider lower section that shields the bottles to reduce turbulence. With standard round bottles and cages the team saw performance improvements, but they decided to push further: this is where the Aerokit project took shape. In partnership with hydration specialists Elite, Wilier developed an integrated system of tapered aero bottles with custom cages specifically for this frame. The CFD results were unambiguous: with the Aerokit, drag was reduced by over two thirds compared to the previous version; even with standard bottles on the new frame, drag was less than half of the earlier model. Beyond numbers, the system holds 1,100ml (via two bottles) and can be swapped for traditional round bottles for race support situations.
With the experience gained in the development of the Supersonica SLR TT bike, Wilier redeveloped the seatpost for the Filante SLR ID2, featuring a slender and sharp profile (38mm x 16mm), it optimises aerodynamic penetration without compromising stiffness and vibration absorption. The Shimano Di2 battery was relocated to the bottom bracket area, thanks in part to the slender seatpost design – improving accessibility and lowering the centre of gravity for better handling.
Wilier kept the design language of the previous Filante for the rear triangle – wide stays meet the seat tube in a broken line. Except the stays are now inclined inward by 2.5° after analysis of the dynamic interactions with the rider’s legs during pedalling. Now, a combination of the new lowered bottle position and the redesigned stays generates a cleaner, more regular flow. Additionally, the chainstay length is slightly increased to allow tyre clearance up to 34mm and new transmission options with UDH compatibility. The front derailleur mount is removable so the drivetrain can also be configured as a 1x setup, accommodating chainrings with up to 56 teeth for the cleanest, most modern aesthetic, the lowest weight and the purest racing experience.
With the Groupama FDJ pros involved, the Filante SLR ID2’s geometry was reworked. The AccuFit system ensures continuity of rider position across sizes, so that from XS or XXL handling is identical. Additionally, there are dedicated handlebar dimensions for each size; reach and drop remain constant across variants, while the low grip ergonomics remain uniform. There are six frame sizes, seven handlebar spacer combinations, five stem sizes, two seatpost versions, meaning 420 fitting configurations are possible, each differing from the next by a mere 2mm. It’s practically a bespoke fitting.
Working with composites world leader Toray, three types of carbon fibre (T800, T1100, M46JB) were deployed for optimum performance. The result: in a Dura-Ace Di2 build the bike weighs 7.1kg. At the Silverstone Sports Engineering Hub wind tunnel the Filante SLR ID2 exceeded its CFD simulation predictions: compared with the Filante SLR ID1, drag reduction for the bike alone was -13.6 per cent (versus -12 per cent estimated). In the bike-rider system it was -4.5 per cent (versus -3.6 per cent predicted). Then, when compared with five top-range WorldTour bikes, it recorded an improved average drag coefficient (CdA) of 2.42 per cent. At professional speeds that adds up to an unequivocal competitive advantage.
For Wilier, the Filante SLR ID2 isn’t just a bike; it is the continuation of the brand’s creed, of a philosophy that has guided its way of building bicycles for 120 years. This culture drives every project, pushing Wilier beyond performance for its own sake towards conscious research that unites experience, genius and technology. “Our goal is perfect motion,” says Wilier, “that harmonious balance between rider and bicycle where force, precision, aesthetics, and function merge.”
With the Filante SLR ID2, it has transformed data not only into motion but into emotion. “The numbers do not represent the finish line, but the starting point for creating bicycles that truly communicate with those who ride them. This is how we keep to a promise that has always accompanied us: to create the means for you to become the fastest version of yourself.”
THE COLOUR OF SPEED
Wilier is renowned for its powerful use of colour – think of the iconic ‘Ramata’ coppery red colour that made its bikes instantly recognisable back as far as the 1940s. Then, in 2024, Mark Cavendish’s famous custom paint scheme that represented all the jerseys he wore in his long career.
Aesthetics are of course an element in that harmonious balance between rider and bike, and for the Filante SLR ID2 Wilier has chosen colours that enhance the frame’s sleek silhouette: “In the sunlight, every shade reveals its strength, expressing the essence of speed… an energy that flows over the shapes and transforms performance into emotion.”
There are five colours available at launch. With each one, the paint makes way for exposed carbon on the upper part of the frame, which Willier says “amplifies a perception of dynamism, tracing a visual dialogue between the seatpost and handlebar.”
Solar Bronze almost recalls the original Ramata scheme, with warm tones that capture the light and return it in metallic reflections that change with every angle. Meanwhile, Pure White is clean, dazzling and like riding inside the light itself – a “living mirror that appears to move with you”. Aurora Blue is regal and glows like the dawn, streaked with red and gold. Lunar Grey is inspired by the moon’s reflection, while Eclipse Black is designed to transmit absolute elegance, silent power, and a touch of mystery, amplifying everything around it.
