Full carbon aero wheels like that have a normal carbon rim. The wide carbon part that you see is an extremely thin piece of carbon fiber and has no structural purpose, but is solely for aerodynamics. the carbon aero part it usually attached to the rim right under the braking surface, but im not sure about this wheel as it is a disk wheel...
now this is where downhill taking an revolution i dont hope going to happend.... i think downhill and freeride as an sport where the bikes can weight what they want to.. aerodynamic is something the road racers use ! i dont hope this is going to be downhill fasion ;o
now some good sides (: it looks good (not the front thing) but i would never buy that.
So you say that carbon fibre is totally weightless? You believe the hype waaay to much... It's said that it's only a cover placed on the normal rims, so there is ALWAYS a weight penalty. And while teams are putting Al/Ti bolts everywhere possible to save couple grams, putting such huge panels on the wheels (where rotary mass counts twice) IS noticable weight penalty for sure.
I doubt if the aerodynamic advantage of these wheels is worth the weight penalty... But probably they know better. We will see the finals results soon.
Trek riders were seen wondering too close to the 'velodrome' with 8.75 inch full travel bikes.........LOL. Hope they have zero cross winds or what's the point. Good Luck Team Trek!