
Installation Guide: RD-RX805 / RD-RX815 / RD-RX817 Di2 Rear Derailleur
Read how to install the RD-RX805 / RD-RX815 / RD-RX817 Di2 rear derailleurs.
If you've been looking at GRX Di2 components you may have seen that there are two rear deraileurs. This RD-RX815 and the RD-RX817.
While the RD-RX817 supports a greater cassette range of 11-42T, that specific derailleur is not meant to be used with a front derailleur. It is the 1x-only GRX rear derailleur.
So if you want to use GRX Di2 and run a front derailleur, this RD-RX815 is the way to go. It has a total capacity of 38T, with a top sprocket max of 11T and a low sprocket max of 34T (min 30T).
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).
Read how to install the RD-RX805 / RD-RX815 / RD-RX817 Di2 rear derailleurs.
Indexing, trimming, or fine-tuning Di2 rear derailleurs is done through micro-adjustment. Read how to set up your Di2 rear derailleur perfectly and ride without those grinding noises.