Shimano's Deore Shadow Rear Derailleur is ready for mountain bike action. The Shadow design tucks the rear derailleur closer in to the wheel, reducing damage from rocks, roots, and trail obstacles. When it comes to gear changes, Shimano's Dyna-Sys supplies consistent, smooth shifting across the entire cassette.
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.