Shimano

XT Dyna-Sys RD-M781 Rear Derailleur

The Shimano XT Dyna-Sys RD-M781 Rear Derailleur sees a continuance of its predecessor's long history of precision, durability, and a low overall weight. It's a crucial part of the Dyna-Sys 10-speed drivetrain system, and of course, Dyna-Sys provides the exact shifting and range of gears that your mountain rig needs.

The XT derailleur design holds a number of improvements over conventional derailleurs. Firstly, the profile is reduced, meaning the XT Derailleur is less likely to get knocked around by trees and rocks. Secondly, and our favorite improvement, a more direct cable path. Your housing enters the stop on the derailleur without the traditional loop of excess housing that's long been the victim of contamination and grabby brush. Additionally, the new M781 design features Shimano's Direct Mount system for increased stability and compatibility with thru-axle systems. You'll also find that the M781 uses Shimano's venerable Shadow+ clutch in order to eliminate chain slap. Combined, these two features alone make the XT the ideal rear derailleur for all-mountain riding.

Shimano uses tried-and-true aluminum components in the XT derailleurs. All of the knuckles, linkage plates, and cage sides are made from it. So, while it may lack the wow factor of the carbon fiber-laden XTR Shadow, it's far more affordable. And when you've been running XT derailleurs as long as we have, you'll know that you'll get a plenitude of perfect, functional mileage on it.

The Shimano XT Dyna-Sys RD-M781 Rear Derailleur is available in the color Black and in both a Long and Medium cage length. The length of the cage determines the overall chain-wrap capacity, or more simply put, how big of a tooth difference it can accommodate between the biggest gear and the smallest gear. Total difference can be found with this equation: big ring - small ring + big cog - small cog. For example, the long cage (SGS) option will work with a 24/32/42 tooth chainring configuration (18t difference) plus an 11/36 cassette out back (25t difference). This meets the maximum chain-wrap capacity of the long cage derailleur at 43t. The Short length cage (GS) has a chain-wrap capacity of 35t and could be used for a single or double ring/bash-guard set-up as the 11/36 (25t difference) plus the 24/32 chainring (8t difference) does not exceed its range.