Double Barrel on the 2013 Ghost Downhill 9000
The raw coloured Downhill 9000 sits at the top of Ghost's two bike DH lineup, and it shows with its top tier spec. A Kashima-treated FOX 40 RC2 graces the front of the bike, with a Cane Creek Double Barrel out back that makes for a no-excuses suspension package. Other highlights include SRAM's X0 DH cranks, and a very German set of Tune hubs. But the admittedly impressive spec is hung from an even more impressive frame - note the carbon fiber rocker arm - who's most obvious standout feature is the idler wheel that routes the chain high above the chain ring. This arrangement hasn't been done for appearances sake, though, with its purpose being to have torque from the drivetrain roughly inline with the bike's extraordinarily high main pivot in order to keep the suspension active and unaffected when the rider is on the gas.
Why go to all that trouble when it would be easier to simply locate the main pivot a few inches lower and inline with the top of the chain ring? It's all about allowing the rear wheel to move out of the way of bumps as easily as possible, a trait that is greatly helped by employing a relatively rearward axle path (through at least part of the travel) that allows the rear wheel to move back and away rather than having to travel in a more upwards fashion. The idler wheel allows Ghost to design a bike that takes this approach to the extreme, but without the negative drivetrain feedback that would otherwise render the bike a dud - removing the idler and would not only result in a hell of a lot of noise (the chain would make contact with the chainstay), but it would also greatly stiffen the suspension under pedalling loads while forcing it jack up through its travel. But with the idler in place the bike likely pedals quite neutrally regardless of the pivot location.
2013 sees Ghost make two notable changes to the Downhill frame, one weight related and one intended to increase the bike' efficiency. They have managed to remove approximately 600 grams, that's 1.3lbs, from the frame, with most of the reduction down to a re-working of the forged, one-piece bottom bracket/ISCG-05/lower shock mount unit. On top of that, they have greatly reduced chain tension as well. The bike's idler wheel layout requires an MRP chain guide with a custom wide-spread boomerang to postion the upper and lower sliders in the correct orientation, with the 2013 version utilizing an even wider slider positioning that brings chain tension figures down to a more normal region.