Troy Brosnan and Aaron Gwin are both using Specialized's all-new S-Works Demo 650b at the World Cup round in Windham, New York - James Huang / Immediate Media
The single-sided seat tube and 27.5in wheels are gathering up much of the attention, but what you really should be paying attention to is the radically redesigned, all-carbon rear end - James Huang / Immediate Media
While the current Demo rear end is effectively two linkages in one (with the inner one driving the rear shock), the new setup is far simpler. The rear shock is driven directly by the upper link and the main pivot is now concentric with the oversized bottom bracket - James Huang / Immediate Media
Notice anything missing here? Yep, whereas the previous Demo had a main pivot located just above and behind the bottom bracket, the new one features a simpler concentric design. The updated kinematics should yield a more rearward axle path than before for better squared-edged bump performance, plus the pared-down, all-carbon design should yield major improvements in terms of stiffness and weight - James Huang / Immediate Media
The back half of the main triangle - arguably the heart of the bike - looks massive, suggesting that the frame will be very stiff from front-to-back for precise handling. Bump stops are built into the carbon fiber front triangle, although neither Aaron Gwin nor Troy Brosnan were using them at Windham - James Huang / Immediate Media
Specialized previously announced a new 27.5in size for the Butcher Control but it's now clearly joined by a burlier DH version with a more heavily reinforced casing for gravity use - James Huang / Immediate Media
Specialized recently released a few teaser images of its new 2015 S-Works Demo downhill machine and most people have been fixated on the move to 27.5in wheels and the visually dramatic asymmetric carbon main frame. However, what you all should really be paying attention to is the radically re-engineered rear end, which suggests better impact performance plus major improvements in weight and frame stiffness.
Troy brosnan and aaron gwin are both using specialized's all-new s-works demo 650b at the world cup round in windham, new york: troy brosnan and aaron gwin are both using specialized's all-new s-works demo 650b at the world cup round in windham, new york
Both Troy Brosnan and Aaron Gwin are racing in Windham, New York aboard Specialized's new S-Works Demo 650b
The new Demo continues on with Specialized's long-running Horst Link four-bar linkage but aside from the basic layout, it bears little resemblance to the current version. The existing Demo is built around a sort of linkage-within-a-linkage system whereby the rear shock is effectively driven by its own miniature rear triangle and the rear wheel following a traditional four-bar axle path around it.
While the current demo rear end is effectively two linkages in one (with the inner one driving the rear shock), the new setup is far simpler. the rear shock is driven directly by the upper link and the main pivot is now concentric with the oversized bottom bracket: while the current demo rear end is effectively two linkages in one (with the inner one driving the rear shock), the new setup is far simpler. the rear shock is driven directly by the upper link and the main pivot is now concentric with the oversized bottom bracket
The new rear end is vastly simplified as compared to the current version
This new layout is vastly simplified with the rear shock now driven directly by the upper link and the main pivot moving from just behind and above the bottom bracket to a concentric design that rotates about a newly oversized shell. Although we don't yet know the width of that new bottom bracket assembly, we do know that it surrounds a 30mm-diameter spindle with a length possibly measuring in between the current BB386EVO and common fat bike standards.
The back half of the main triangle - arguably the heart of the bike - looks massive, suggesting that the frame will be very stiff from front-to-back for precise handling. bump stops are built into the carbon fiber front triangle, although neither aaron gwin nor troy brosnan were using them at windham: the back half of the main triangle - arguably the heart of the bike - looks massive, suggesting that the frame will be very stiff from front-to-back for precise handling. bump stops are built into the carbon fiber front triangle, although neither aaron gwin nor troy brosnan were using them at windham
The new concentric main pivot surrounds a newly oversized bottom bracket shell
Whereas the current flagship Demo uses a carbon fiber front triangle and a welded aluminum rear end, this new version is carbon all around – including the seatstays, chainstays, and the enormous upper link. Cross-sections grow tremendously as compared to the current Demo, too, and pivot diameters look to have puffed up as well.
Taken in total with the absolutely massive rear half of the front triangle, we anticipate major gains in rigidity along with big weight savings – possibly on the order of half a kilogram (1.1lb) or so. The new pivot layout also looks like it'll produce a more rearward axle path for better square-edged bump performance.
Notice anything missing here? yep, whereas the previous demo had a main pivot located just above and behind the bottom bracket, the new one features a simpler concentric design. the updated kinematics should yield a more rearward axle path than before for better squared-edged bump performance, plus the pared-down, all-carbon design should yield major improvements in terms of stiffness and weight: notice anything missing here? yep, whereas the previous demo had a main pivot located just above and behind the bottom bracket, the new one features a simpler concentric design. the updated kinematics should yield a more rearward axle path than before for better squared-edged bump performance, plus the pared-down, all-carbon design should yield major improvements in terms of stiffness and weight
The new rear end should be both dramatically lighter and much more rigid than the old one
Other details include internal cable routing through the main triangle, a molded guard for the underside of the down tube, a move from IS rear brake tabs to post mounts (sized for 180-203mm rotors), and integrated bolt-on bump stops just behind the head tube.
Specialized previously announced a new 27.5in size for the butcher control but it's now clearly joined by a burlier dh version with a more heavily reinforced casing for gravity use: specialized previously announced a new 27.5in size for the butcher control but it's now clearly joined by a burlier dh version with a more heavily reinforced casing for gravity use
We spotted a new DH-specific version of Specialized's recently announced 650b Butcher tire
Specialized remains mum on technical details on the new Demo so for now, we can only speculate that our observations are correct. Even if we're only half right, though, the 2015 Demo looks to be a massive improvement over the old one. Stay tuned for official details coming soon.
James Huang is BikeRadar's former technical editor. After leaving BikeRadar in 2016, he worked at CyclingTips and Escape Collective. He now runs the Substack cycling publication N-1 Bikes.
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