Zerode G-1 mountain bke
The first and freakiest thing one notices about the dual-suspension downhill bike is its drivetrain. Instead of the usual single chain reaching from the chainrings directly back to the cassette, it has two - one goes from the single chainring up to a midships-mounted Shimano Alfine internal geared hub, then another goes from that back to the rear hub. On a normal internally-geared bike, the Alfine would be the rear hub.
There are several good reasons to be using a mechanism like the Alfine, regardless of its location. For starters, it's much less fragile than a rear derailleur, and is relatively unaffected by mud and gravel. It can also shift easily under full chain load, or even when the bike is stopped. Additionally, chains will last longer, as they don't have to slide up and down a series of sprockets.
There are also a few reasons why internal geared hubs aren't more commonly used on mountain bikes, one of them being that the axles of such hubs typically aren't as strong as those of conventional hubs - but when not mounted on the wheel as is the case with the Zerode G-1, high axle strength isn't crucial.
Source: gizmag.comAdded: 23 May 2011