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.
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.
Check out more of our Specialized 2015 coverage.
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 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.
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.
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.