First off, I thought it has been well established via the Ridemonkey WC E-spec Team that a Demo is in fact not a real "downhill" bike given the devastation it has wrought upon one Aaron Gwin. So my point stands
Actually, I thought about the Demo as I was typing my earlier response, and thought they had switched to 150 mm. But now that I think about it, this is the company that still (stubbornly) doesn't have a 650 bike, so maybe they are going to address a lot of standardization issues all at once...650 All-Enduro-Trail bike, 150 mm rear Demo, and non-proprietary shocks.
That's one good reason. Another is to easily build a zero dish (stronger) rear wheel. I can only guess that they are doing 135 on the S-Works to save whatever small amount of weight they can from the narrower hub/rear triangle and maybe they can do a zero dish wheel with the 7-speed cassette on there.
Basically yes, but in reverse order. 83mm BBs were a response to 150mm hubs in order to keep the chainline reasonable. 150mm hubs were originally introduced to increase the flange spacing of hubs in order to stiffen and strengthen the wheel laterally. Unlike 135mm hubs, it's feasible to build 150mm hubs with the flanges spaced evenly either side of the centreline, allowing zero-dish wheels to be built. This does involve pulling the non-drive-side flange in a bit (so overall flange spacing between 150 and 135 isn't much different), and for a while there were also 165mm rear ends (as used by Giant and Iron Horse before the Sunday) that allowed for super wide hub flange spacing but also required a 100mm BB shell to work properly. Those were awesome for having a stable stance on the pedals, but it made the actual pedaling action really weird and gimp-like, and they also sat your derailleur/frame/axle out quite a way, making derailleur destruction even easier.
I was/am not a fan of wide bbs. I didn't like the 100 on my dh bike, nor the one on my fat bike, and I thought the 83mm one was really only passable. I much preferred the 73 if you actually wanna pedal. I never had too much trouble with wheel strength as long as they were properly built.
Its technically the 1st in the UK but still nothing on the site or facebook, looks as if the there are some front triangles hanging here..................Im guessing a tweak in Geo and maybe some weight saving maybe and 27.5" compatible
There is a price on the site which says £1999 pretty sure they were £2399 when they came out the first time round.