This is old news. This setup was used by Jalabert and Pantani also back in the mid 90's. It's primarily for weight savings and simplicity. On the mountain stages it's all little ring up and big ring down.
Julian Shapiro
Sag Harbor, NY
> For many of you it may be no supprise, but I was shocked to find out
> yesterday that for mountain stages, Armstrong has used and intends to use
> a DT shifter for the front chainring. Apparently, he finds SIS shifting
> too risky and too hard to control for front derailleur trimming. He still
> prefers shifting on the fly for his rear derailleur. I wonder if this is
> the beginning of a retro trend which will start with DT derailleurs and
> end with steel lugged frames. I understand that there are no steel frame
> manufacturers that are able to sponsor a TDF attempt, but perhaps Trek can
> charge $3.000 for a high quality Aluminum or Carbon Fiber road bike and
> $5,000 for a down tube shifted steel lugged model with 1 inch threaded
> steering tubes thrown in just for increased aerodynamic advantage. It may
> even turn out that a 6 cog rear cluster is more efficient in that it saves
> weight and allows for a narrower rear end.
>
> Garth Libre in Miami Shores Fl.