The Fort William downhill track is a brutal one, with a surface that looks like a cobblestone street after an earthquake. Specialized's Miranda Miller will be taking on the high speed, rock-riddled course aboard a 29”-wheeled prototype, the same bike that we first caught a glimpse
of at the Whistler Bike Park last week. Loic Bruni and Finn Iles will be sticking to their 27.5” Demo races bikes, but I'm sure they'll be spending time on this yet-to-be-released machine in the near future.
The frame design is a distinct departure from the current Demo – it's no longer one-sided, and there's also no concentric bottom bracket pivot to be seen. Instead, the shock is driven by a vertical link that's attached to the seat stays and a horizontal link that's attached to the main pivot. The design keeps the shock positioned close to the bottom bracket, which should keep the bike's center of gravity nice and low.
The concentric BB pivot may be gone, but it does look like an eccentric bottom bracket has been installed, although I doubt that's something that would make it into a production model. Eccentric bottom brackets are more typically used to adjust the chain tension on singlespeed bikes without horizontal dropouts, but they can also be used to adjust a bike's geometry – the BB height and chainstay length can be altered by rotating the device inside the bottom bracket shell. Miranda's bike also has what looks like a flip chip at the front shock mount. It's currently in the middle setting, but I'd be willing to be that there's a high and low option as well, at least for this particular frame.