Shimano XTR Race M980 10 Speed Rear Derailleur

Part of the brand new 10 speed XTR groupset, the Shimano M980 rear derailleur is engineered specifically to work with 10 speed Dyna-Sys drivetrains. It features a number of substantial upgrades over the XT rear derailleur and previous XTR versions, though most noticeable is the redesigned linkage geometry that provides a more linear feel throughout the range of the cassette. Being the top of the range line from Shimano, XTR gets all of the Japanese Juggernauts technology, R&D and World Cup level testing poured into it to create the lightest, fastest and most efficient groupset available. Dropping weight down to just 175 grams with a carbon fiber cage, the XTR rear derailleur will satisfy both weight weenies as well as trail riders who are searching for shifting nirvana. 

The Dyna-Sys design ethos is based around drivetrain efficiency, stability and on-the-trail usability and a quick look at any of the 10 speed components from Shimano will give you evidence of that. Based around a 10 speed wide-range cassette, you will find yourself shifting less up front and using more of the gears out back with a Dyna-Sys drivetrain, which makes the XTR rear derailleur a vital part of the overall shifting quality. The M980 retains the Shadow low-profile design as the previous model, but the new Long Arm construction makes for a more linear cable pull that increases consistency through the range of the cassette. As you'll find yourself shifting more with the rear, this new linear feel and the snappier return spring become easy to appreciate, especially in the smaller sprockets. The M980 derailleur is designed to work with both a triple and double crankset, though for optimum performance you should select the shorter Medium cage for your 2x10 setup and the Long cage for your 3x10 drivetrain. Due to the cable-pull ratio, the M980 will only work with Shimano Dyna-Sys shifters, though you can use it with either Shimano or SRAM 10 speed chains & cassettes. With an upgrade to sealed cartridge bearings for both top and lower jockey wheels, the XTR rear derailleur is engineered to perform flawlessly in all sorts of conditions.

From Shimano:

"The new 10-speed XTR rear derailleur sees a re-engineered architecture that provides a smooth, linear feel at the shifter and is remarkably stable despite suspension movement, trail chatter or inevitable cable contamination".