Rear Derailleur (1x)

Rear Derailleur (1x)


If you've been looking at GRX Di2 components you may have seen that there are two rear deraileurs. This RD-RX817 and its lightweight cousin, the RD-RX815.

The RD-RX817 was developed by Shimano specifically for use in 1x bikes. This means that running this rear derailleur with a front derailleur is officially not supported. There are reports of users installing a front derailleur anyway, like this user on If you do, keep in mind that this is not Shimano approved and your shifting quality could suffer.

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This RD-RX817 has a total capacity of 31T, allowing you to run an 11-42T cassette. Its top sprocket max is 11T and the low sprocket max is 42T (min 40T).

Both GRX rear derailleurs feature a clutch mechanism, just like the Ultegra RD-RX805 and the mountain bike rear derailleurs. Shimano call this the chain stabiliser. It can be adjusted and prevents chain slapping (or worse, dropping your chain).


  • Model code: RD-RX817
  • Series: GRX (RX815)
  • Weight: 318g
  • Speeds: 11
  • SD50 ports: 1
  • Total capacity: 31T
  • Low sprocket max: 42T
  • Low sprocket min: 40T
  • Top sprocket min: 11T
  • Top sprocket max: 11T
  • Pulley teeth: 11
  • RD type: Shadow RD+
  • Clutch: Yes

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Rear Derailleur (2x)

View the Hydraulic Disc Brake Dual Control Lever (ST-RX815)


Hydraulic Disc Brake Dual Control Lever

View the Front Derailleur (FD-RX815-F)


Front Derailleur

View the Internal Battery (BT-DN110)


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