Who invented it? BMC ignites a firework of innovation with the Fourstroke
The new Fourstroke has a modern look: the race fully with 100 millimetres of travel naturally has 29er wheels, a slack steering angle of 67.5 degrees, a long front end, a steep seat angle of 75.5 degrees and short chainstays of 429 millimetres. But there is much more to the new bike than modern geometry.
The Fourstroke 01 is designed with a redesigned frame for unprecedented power delivery, characterized by torsional and bottom bracket stiffness. The revised APS (Advance Pivot System) delivers pedaling efficiency, traction and control on modern cross country race tracks. APS is based on two short rocker arms that move concentrically to each other, creating a wheel lift curve. According to BMC, the result is a perfect balance of fully active braking behavior, a minimal kickback effect and a sensitive response.Unique selling point: the dropper seatpost
The new Race Application Dropper seatpost (RAD) stands out in particular. This shows a high level of system integration with the frame, is extremely light at 345 grams and offers a decent drop of 90 millimetres to find the optimum riding position on fast uphill and, of course, downhill courses. The two-position adjustment of the dropper post is designed to simplify the operation of the dropper post, giving you a decisive advantage in races. Peter Stämpfli, Mountain Bike Engineer at BMC Switzerland, explains the technical details, which have little in common with the design of conventional dropper posts: "The integrated design gives us the opportunity to move away from the round shape of the seatpost and push the boundaries of conventional seatpost design."
In contrast to conventional round seatposts, the RAD seatpost was designed in an elliptical shape and is therefore more stress-resistant. In addition, the shape reduces the weight and improves the strength for low deformation and uncompromising functionality under load. According to BMC, different wall thicknesses offer the perfect balance between the forces caused by the rider and a low weight. Thanks to the integration of the components, the seatpost also scores with a functional, clean look.The saddle height is adjusted in the same way as with conventional systems and does not require the seatpost to be shortened. Thanks to an oversized air chamber, the RAD-Post works with low air pressure. This reduces the pressure on the air seals and makes maintenance less intensive. The BMC post is completely mechanically driven and has no hydraulic parts - according to the Grechner bike builders, this guarantees super easy servicing.Every gram counts
The Fourstroke 01 was redesigned from the ground up with great attention to detail - the Impec laboratory at the company headquarters in Grenchen played a decisive role in this. According to BMC, a small number of individual components extend the bike's maintenance cycles and improve the overall weight. For example, it was possible to integrate a dropper seat post and still maintain a low weight of 2,575g (including RAD seat post and hardware). The optimized chassis reduces the number of installed parts. This not only improves reliability, but also saves 51g in weight compared to the previous Fourstroke 01. Integrated headset shells promise a weight saving of 20 grams compared to external shells. The super-light thru-axle developed in the Impec Lab saves an additional 9 grams of weight and the completely new carbon upper link is the stiffest connection between the front frame triangle and the swingarm. This ensures uncompromising suspension performance and a 40g weight saving compared to an aluminum upper link.
Details that make the difference
The integrated and lightweight fork stop in combination with the straight down tube design leads to improved stiffness at the front. In addition, the optimized cable routing and the revised frame protection support the clean lines of the Fourstroke 01. The Mud Protector on the lower rocker arm increases the longevity of the bearings. The integrated chainstay protector and the lightweight chain guide make the bike suitable for racing. The internal cable routing is routed completely through the front frame triangle, the lower rocker arm and the swingarm for quick and easy maintenance.
Sizes and models
The new Fourstroke is available in the following model variants: Fourstroke 01 ONE, Fourstroke 01 TWO, Fourstroke 01 THREE and Fourstroke 01 Framset. Each model is available in sizes S, M, L and XL.
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Note: This content has been automatically translated from German. Please report any incorrect translations.