Shimano Dura Ace RD-7900 Rear Derailleur

Shimano's dominant position in the bike industry is based foremost on one simple fact: They can forge metals with a creativity and sophistication far beyond anything their competitors can dream. Shimano factories are crammed with VW Bug-sized forging machines that spend all day long pounding alloys into highly precise little bits that -- after final assembly -- make a Dura-Ace bike brake and shift and look so fine. Shimano = Forging. It's as simple as that, and that's the reason why they long resisted the temptation to wander into the world of carbon. The rest of the industry, of course, embraced carbon with an untrammeled cheek-to-cheek, two-arms-and-two-legs enthusiasm, and while they were at it, they accused Shimano of being a fuddy-duudy for not doing the same. Shimano's position was simple: Anything carbon can do, forged metal can do better -- lightness, durability, cost, you name it.Still, there's something cosmetically sexy about carbon. And market trends are what they are -- consumers vote with their wallets, and they're choosing carbon. With the Dura-Ace 7900 series components, Shimano proves that while they may move deliberately, they are most definitely not fuddy-duddies. Case in point, the Dura-Ace RD-7900 rear derailleur --The Dura-Ace RD-7900 is Shimano's first ever rear derailleur that makes use of carbon fiber. The pulley cage and P-body are both made of carbon to shave off 16g in comparison to the RD-7800 rear derailleur. Shimano states that their choice of carbon vs. alloy here has no detrimental effect to long-term durability of the derailleur. And while the carbon vs. alloy debate has a timelessness to it akin to Red Sox vs. Yankees, there's something else going on with the RD-7900 that -- at least to us -- is far bigger news: It has an expanded chain wrap capacity in comparison to the RD-7800. What's chain wrap capacity It's a simple math equation: (Big ring - Small ring) (Big cog - Small cog) = Chain Wrap Capacity.