Shimano blows us away again with the XTR Shadow Plus 10-speed rear derailleur. The Shadow design is already well known and loved for its direct cable routing and low profile that greatly lessens the risk of snagging your cable on roots or tagging your derailleur on rocks. Shimano's Plus derailleur technology is a one-way clutch system that stabilizes the cage and your chain when ripping over rough terrain. Chain slap and noise is virtually eliminated and dropped chains are practically a thing of the past. Of course, it retains XTR's legendary smoothness, light action and super precise shifting. Once you ride a Plus derailleur, you'll never want to ride without it!
An important part of a rear derailleur's job is keeping the chain taut as you change gears. Chain-wrap capacity is a number that tells whether or not a derailleur will be able to do this on the drivetrain you plan to use it on. Calculate chain-wrap capacity with this formula: Chain-wrap capacity = (large chainring - small chainring) + (large rear cog - small rear cog). Example: 44/29 chainrings and a 11-28 cassette: (44 - 29 = 15) + (28 - 11 = 17) = 32-tooth chain-wrap capacity.