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Shimano GRX RD-RX815 11-Speed Di2 Rear Derailleur
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Shimano GRX RD-RX815 11-Speed Di2 Rear Derailleur


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Mfg PartNum: IRDRX815
MSRP: $299.99
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GRX RD-RX815 11-Speed Di2 Rear Derailleur

The Shimano GRX 11-Speed Di2 rear derailleur brings mountain bike technology to gravel riding with a clutch equipped rear derailleur allowing smooth shifting on rough terrain. The Shadow RD Technology utilizes it's race-proven, low-profile design to offer a derailleur that is more compact and fits closer to the frame, ensuring less damage in a crash. With the adjustable chain stabilizer, chain slapping and dropping are prevented while the gravel-tuned clutch tension provides silent and uninterrupted electronic rear shifting on the roughest terrain.


  • Operates with Shimano Di2 for digital electronic shifting
  • Toggle clutch ON/OFF to match the terrain
  • Gravel-tuned clutch tension provides smooth and reliable mixed surface shifting
  • Switch stabilizer ON/OFF to match the terrain
  • For 1x and 2x drivetrains

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.

The product weight specified is an approximate weight based on the manufacturer's specifications (if available) or our measurement of one or two examples. For most products, the weight will typically vary by 5% to 10%.


Mfg PartNum: RD-RX815 


Total Capacity: 38T 

Max. front difference: 17T 

Top sprocket: 11T/Min. 11T 

Low sprocket: Max. 34T/Min. 30T 

Top-Normal Spring Type: SHADOW RD plus 

Weight: 287 g 

Actuation: Electronic 

Discipline: Road/Gravel 

Mount Type: Standard Rear Hanger 

Speed: 11 


Ordered by Most Relevant First
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Reviewed 10/22/2020
by J Stew
Cycling Enthusiast
New Jersey
Value Rating
Overall Rating
4 of 4 customers found this review helpful.
Shimano continues to NOT disappoint!

I was really torn between going with SRAM Force eTap and Shimano GRX Di2.

I currently use Ultegra Di2 on a road bike and it has almost never failed me. On the rare occasion that it has, it was due to a jockey wheel needing to be replaced or an alignment issue. Shimano really paved the way for electronic shifting and they haven't skipped a beat with GRX. I ultimately decided to go with Shimano because of my experience with Ultegra. I really liked the idea of having one battery to charge and in terms of battery life I have never had an issue with running out of battery while on the road. I realize this is just down to an individual remembering to charge the battery, but I really only find myself charging the battery maybe once every month. I figured that if I really was doing a backcountry ride where I was going to blow through a 1500-2000 mile battery without the ability to recharge, then at that point I can always carry a spare battery. While it's not as easy to swap out batteries compared to SRAM, with it stored in the seatpost it wouldn't be a situation that I couldn't do it.

Another reason I went with Shimano is due to replacement costs. Derailleurs, if needed to be replaced, are simply just cheaper.

I will have to say that getting all the Shimano parts was a PAIN IN THE ASS! This is largely due to supply chain disruptions around COVID, however Bike Tires Direct was solid in being able to get most of them. I welcome BTD to reach out to me with any questions around my experience (good/bad/neutral) - I'm def excited to look their way for future needs. Inventory and customer service are amazing in my experience.


One of the things I really liked about SRAM was the setup. Basically wire-free. However, I figured that this is a one-time deal and considering I'm not traveling too much with my bike I viewed this really as a set it and forget deal. I'm also very confident in my mechanic's ability to set up Shimano and so I didn't want to base my decision on this.

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Reviewed 6/1/2023
by Anonymous
Overall Rating
Shimano simply the best

Great DI2 rear derailleur changed to the GRX from Dura Ace it's every bit as good and handles the wider range cassette with ease

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