Shimano

XTR Shadow Plus RD-M986 Rear Derailleur

The smooth action of Shimano's XTR Rear Derailleur has always been a contributing factor to XTR's legendary status. But the Shadow Plus RD-M986 packs a new feature that's rewriting drivetrain performance -- a motion damping switch that controls pulley cage fore and aft movement.

This means you can turn on and off the damper via the gold switch located by the upper pulley. with this turned to the on position, the cage resists forward motion to retain tension within the drivetrain. This prevents dropped chains and chain slap. The switch can be fine-tuned as well. An included tool, neatly stored in the derailleur itself, allows you to increase or decrease the amount of tension for varying frame designs and rider preference. This switch builds on the existing M980 Shadow platform.

This means the M986 has the same low-profile geometry that keeps it closer to the dropout and safer from impacts with roots and rocks. Both pulleys now have sealed bearings, and the pulley cage blends a carbon fiber outer with an aluminum inner plate for a just-right combination of light weight, strength, and stiffness. Shimano engineers also changed the return spring so that it works better with full-length cable housing. With the new spring, the XTR Rear Derailleur snaps onto smaller cogs as quickly as you can make the shifts.

You have the choice of a medium cage (GS) or long cage (SGS). The differing lengths of the cages translate into different chainwrap capacities for each version. The GS derailleur is best paired with a 2x10 XTR Crankset. The long cage SGS model has a greater chainwrap capacity, so it will handle the XTR Trail Triple Crank.

The Shimano XTR Shadow Plus Rear Derailleur RD-M986 has a top normal spring configuration, which means that it returns to the top gear when the cable tension is released (which is normal). It's designed to work in harmony with Shimano Dyna-Sys 10-speed Rapidfire shifters and 10-speed cassettes with a maximum 36t large cog.