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ShimanoGRX RD-RX817 Di2 Rear Derailleur


Item # SHIU19G

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  • Black, Rear ($319.99)
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Item # SHIU19G

GRX RD-RX817 Di2 Rear Derailleur

Gravel cycling is a bit of an enigma. While it's mostly new to the scene, it manages to evoke nostalgic feelings that we don't really get from modern road cycling these days. Between wool jerseys, steel frames with drop bars, and a sense of adventure that doesn't stop when the tarmac ends, it manages to captivate us with an undeniable vintage aesthetic. With that said, it's not all about throwing new technology to the side, and Shimano proves it with the GRX RD-RX817 Di2 Rear Derailleur that brings electronic shifting to the gravel scene, built tough enough for life off road, but with silent, uninterrupted shifts that are precise and reliable regardless of the terrain ahead. Like you'll find through the rest of Shimano's GRX rear-derailleur line, the RX817 comes equipped with borrowed technology from the mountain bike world with Shadow clutch mechanism that adjusts chain tension to reduce dropped chains and keep your ride quiet through the rubble.

Following in the footsteps of the revamped Dura-Ace and Ultegra groups, this GRX derailleur gets its Shadow cage treatment placing it closer to the frame and under the cassette keeping it out of harm's way and less likely to take the brunt of a driveside crash. This also allows the derailleur to move in a much more linear path allowing for shorter throws with less effort. The RX817 model comes ready to roll with a medium cage length, which accommodates both Shimano's 11-40t and 11-42t cassettes, allowing for a wide range gear ratio when paired with a double without the usual huge jumps between the cogs like on a 1x setup.

Sticking to what the brand's customers know well, Shimano continues to use the Dura-Ace, Ultegra, and Tiagra designation with the GRX line, with this particular model falling under the Ultegra umbrella, which means it gets the usual materials and finishes that we expect from a groupset that's just one step from the top. Its weight, smoothness, and durability make it more than capable of racing against the competition on course, or the sun to your campsite for the night on a bikepacking trip.

  • A near-silent derailleur that brings modern electronics to gravel
  • Shadow clutch mechanism increases spring tension to eliminate chain slap
  • Clutch is easily flipped to make wheel changes and flat fixes a breeze
  • Derailleur cage tucks closer to frame to avoid hits and bumps
  • Compatibility for both 1x and 2x drivetrains
  • Durable alloy construction handles mud and off-road adventures
  • Works with current Shimano 11-speed road shifter/brake levers
  • Low-profile Shadow design helps avoid damage from impacts
  • Electronic shifting is smooth, crisp, and precise
  • Medium length cage ideal for 11 - 40t and 11 - 42t cassettes

Tech Specs
Pull Type
Cage Length
Cassette Range
11 - 42t, 11 - 40t
Shimano GRX Di2
Recommended Use
Manufacturer Warranty
2 years

Actual Weight

Actual weights are measured in-house by the Competitive Cyclist team.

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Black, Rear

Claimed Weight

Claimed weights are provided by the vendor.

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    Per Shimano, the 815 can be used with 1x and 2x, but the 817 is 1x specific. Your description says it can be used with 1x and 2x. Confirm please.