Keeping your existing wheels when upgrading to 12-speed gravel gearing matters if you've invested in a quality wheelset, and the Shimano GRX RD-RX820 makes that possible. Unlike the 1x12 GRX derailleurs that require Micro Spline freehub bodies for their 10-tooth top cogs, the RD-RX820 works with standard HG cassettes in 11-34T and 11-36T configurations. That means your current wheels with HG freehubs stay in the rotation, and you avoid the cost and hassle of swapping freehub bodies or building new wheels.

The RD-RX820 is the 2x12 derailleur in the GRX 12-speed lineup, designed to pair with the FC-RX820-2 crankset and its 48/31T chainrings. Shimano calls this setup "Undroppable" in their marketing, referencing the double chainring configuration that eliminates chain drop concerns inherent to some 1x setups. The tighter gear steps on an 11-36T cassette compared to the wide-range 10-45T or 10-51T cassettes used with 1x drivetrains appeal to riders who want precise cadence control during racing or fast group rides. You get enough range for gravel climbs while maintaining the ability to fine-tune your effort level on rolling terrain.

Shadow RD+ technology tucks the derailleur mechanism closer to the frame for improved ground clearance and crash protection. The integrated chain stabilizer uses a friction clutch to maintain tension through rough sections, which keeps the drivetrain quiet and prevents chain slap on washboard surfaces and choppy descents. The stabilizer includes an ON/OFF switch that lets you disengage the clutch for easier wheel removal during roadside repairs or when loading the bike for transport.... Read More