The Shimano Deore XT RD-M772 Shadow rear derailleur is the biggest and boldest innovation in the new XT line. It takes from some old and established design cues to create a derailleur that shifts crisply yet presents a minimal profile for crashing. A paradigm shift for the derailleur? You decide.

Let's begin with where the derailleur attaches to the dropout. Shimano decided that the derailleur mounting bolt would no longer be where the rear derailleur pivots. The mounting bolt holds a small bracket onto which the derailleur is bolted. The new derailleur mount position is back and a bit lower than the traditional pivot, which allows the derailleur to fit better under the right chain stay, shadowing the cassette. When the chain goes through the derailleur to the smallest cog (aka high gear), the derailleur protrudes 15mm less than a traditional derailleur, a profile that means it barely protrudes past the quick release nut in the dropout above. By almost hiding underneath the nut, the derailleur and chain stay, the derailleur is protected from damage in some crash situations, which both preserves the derailleur and the derailleur hanger.

The news gets better -- this new positioning also allows the cable housing to go in almost a straight line to the housing stop on the derailleur body. With less cable, there's less to hook, less to kink, and it's lighter and makes the derailleur shift faster. It's all good.

Hidden in the pivot is a stronger spring in the swingarm that makes it harder for the derailleur to bounce when riding on rough terrain. Less bounce means less chain slap. In total, a hardy unit for enduro, technical and even freeride applications. And despite the engineering and new design, it is priced the same as the other Deore XT rear derailleurs. Something for nothing? Looks like it.

The Shimano RD-M772 XT Shadow Rear Derailleur has a top-normal design, meaning the spring tension in the derailleur pushes the cog down to the smaller or harder cogs. Aka "traditional," this is the one you grew up with. While it is designed to work with the XT Rapidfire Plus, but will work with Rapidfire, SRAM 2:1 shifters, and in reverse on Shimano DCL (down is up, up is down).

The Shimano Deore XT RD-M772 Shadow rear derailleur is offered in two sizes: GS (mid-cage) and SGS (long-cage). In all cases, the max cogset that can be used is an 11-34. The difference is that the mid cage size has a 33 tooth total capacity while the long cage takes 45 tooth total. All XT rear derailleurs have sealed 11-tooth upper and lower jockey wheels. The spring in the derailleur yields Shimano's traditional "light action" gear changes. 235g (long cage). MSRP $109.99.