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Shimano GRX RD-RX820 2x 12-Speed Rear Derailleur 11-36T
Shimano GRX RD-RX820 2x 12-Speed Rear Derailleur 11-36T
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Shimano GRX RD-RX820 2x 12-Speed Rear Derailleur 1
Shimano GRX RD-RX820 2x 12-Speed Rear Derailleur 2

Shimano GRX RD-RX820 2x 12-Speed Rear Derailleur

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Undroppable — On Any Surface

For riders seeking the best of both worlds, Shimano's new GRX 2x12 RX820 UNDROPPABLE drivetrain utilizes gravel-optimized 48/31 front chainrings paired with an 11-34T or 11-36T cassette. This setup delivers an ultra-wide gear range for spinning a comfortable cadence when cruising the flats, smashing endless dirt road rollers, or tackling a massive backcountry climb.

This option delivers precise mechanical front and rear shifting and features integrated SHADOW RD+chain stabilizer for ultimate drivetrain security over bumpy terrain. It maintains tighter rear cassette gear steps, ideal for subtle cadence changes during competitive racing and spirited weekend group rides. And the 2x12 setup seamlessly interfaces with most existing 700c wheels thanks to its use of the tried-and-true HG freehub body design.

The Next Generation Of Gravel

With the introduction of Shimano GRX RX820 12-speed mechanical components, SHIMANO continues its legacy of innovation as the originator of gravel-specific components. Rooted in simplicity, reliability, and adventure, the new 12-speed GRX lineup delivers more gearing options along with unrivaled ergonomics so riders get the most out each unpaved adventure, wherever that might be. With a focus on the heart and soul of gravel cycling, Shimano mechanical GRX receives this 12-speed upgrade delivering top-tier performance without an over-the-top price. And since gravel is all about personal expression and freedom to choose how and where to ride, Shimano GRX includes three unique 12-speed mechanical drivetrain personalities to cover the full spectrum of riders and rides.


  • 12-speed
  • SHIMANO SHADOW RD+ Chain Stabilization
  • Max cassette range: 36T
  • 270 grams

B-Stock - This product has one or more B-Stock units available. These units can be purchased at a discount (see option select). B-Stock units were returned from other customers and may have missing or damaged packaging materials. These units are otherwise as new. The full manufacturer warranty applies. Click Here for more information.



Mfg PartNum: IRDRX820 


Actuation: Mechanical 


Discipline: Road/Gravel 


Speed: 12 


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As expected
by Anonymous

Once installed and adjusted, this derailleur shifts with typical Shimano perfection.

Note that if routing internally, that is, you have no braze on stops, you will have to buy a shift cable set with long enough housing to reach from the lever to the adjuster on the derailleur.

The short sections Shimano provides with the levers are useless if you have this situation.

I ended up using the inner cable that came with the shifter but bought a cable set just to get a section of outer cable that was long enough to get from the lever, through the frame and to the adjuster on the derailleur.

Reviewed 11/2/2023
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