The Di2 specific RD-RX805 offers the ultimate upgrade for riders using Shimano electronic groups. Compatible with both Dura-Ace and Ultegra Di2, these rear derailleurs usher in yet more MTB technology into this road derailleur to optimized chain tension for a more efficient drivetrain. A simple lever rotates on or off to activate or deactivate the clutch. When activated, the clutch stiffens up the entire rear derailleur assembly for crisp and accurate shifting, then simply deactivate for service or wheel changes. This effective design was first released in mountain bike derailleurs several years ago and has now become a must-have feature on the road and gravel side of things.

The now familiar Shadow design sits much closer to the frame and under the cassette, protecting the cage from ground contact in case of accident or from bike to bike interaction when transporting multiple bikes. The pathway the derailleur action travels when shifted is also more linear, and smooth. A shorter throw now results in quicker, more precise shifts with less effort, even over the wider spread of the 11-34 cassette. Adding that greater range opens more cyclists up to various forms of road cycling, such as gravel, endurance, adventure, etc. One important difference between the mountain and road application of the Shadow design is the very welcome presence of a compact barrel adjuster for manual cable tension adjustments. The B-link standard hanger mount can be uncoupled from the direct mount pivot if your frame accepts the direct mount system.

Classic Ultegra materials and finish means you get a robust derailleur body, links, and axles which are strong and light. Flouric coated link bushings keep the movement smooth and the linkage torsionally stiff and aligned. The cage plates are made from machined aluminum, not CFRP, so you gain a few grams but gain max durability to go along with excellent cage stiffness. The cage design is torsionally and laterally stiff, resulting in reliable shifts and chain performance under load, no matter what ring and cog combination you find yourself in- all the way from 11-34 with the GS version. The upper and lower pulley wheels of the cage have specific profiles, and ride on Stainless Steel bolts that ensure longevity and resist corrosion.