Shimano XTR RD-M986
The Shimano Shadow+ technology of the RD-M986 provides more stability by using a switch, which increases the spring tension and activates a stabilizer which fixes the cage through increased friction, and so also reduces the hitting of the chain in ambitious terrain. This serves not only the noise elimination, but also effectively prevents jumping off the chain.
Chain bouncing can often cause noise as the chain slaps the top and bottom of the chain stay, or even derail from the front chain ring in extreme circumstances. The switch when set to the ON-position dampens the cage and consequent chain movement for a nearly silent and stable riding experience. In the OFF-position it eases the installation and removal of the rear wheel by relaxing the spring tension of the cage.
The Dyna-Sys XTR rear derailleur provides an accurate and effortless shifting performance with increased stability and reliability by minimized external influences. The ultra-low profile design is intended for more aggressive riding because it decreases the risk of damage in narrow passages and risky trails. The rear derailleur performs smoothly and silently under all conditions and with very precise index functions. Furthermore the sealed bearing pulleys reduce friction.