12-speed Di2 New User Guide
Just bought a new 12-speed Di2 bike? This page explains what the buttons do, how to charge, and what synchronized shfit does.
Shadow RD+ Rear Derailleur (12 speed)
GRX RD-RX825
This twelve-speed gravel rear derailleur features a charge port, LED, function button and an EW-SD300 type port used to connect the derailleur to the battery.
Both the rear derailleur and the front derailleur connect to the battery using a wire. The shift levers send their shift commands to the rear derailleur wirelessly.
Since this is a gravel rear derailleur, it also has a clutch mechanism that can be switched on/off. When turned on, this mechanism will ensure proper chain retention and smooth shifting on rough terrain.
Affiliate Links
Using the affiliate links to purchase anything earns the site a small commission, at no additional cost to you.
Just like the 11-speed GRX rear derailleurs, this 12-speed RD-RX825 falls into the road category. This means that it's fully compatible with other 12-speed Di2 groupsets. If you want to build a 12-speed road bike with a clutch rear derailleur, you can!
Specifications
- Model code: RD-RX825
- Series: GRX (RX825)
- Weight: 310
- Speeds: 12
- Number of switches: 1 (function button)
- SD300 ports: 1
- Max front difference: 16
- Total capacity: 41T
- Low sprocket max: 36T
- Low sprocket min: 34T
- Top sprocket min: 11T
- Top sprocket max: 11T
- Wireless connectivity: Bluetooth / ANT
- Charging port: Yes
- Charger: EW-EC300
- RD type: Shadow RD+
- Clutch: Yes
Related components
View all componentsRelated pages
12-speed Rear Derailleur installation and adjustment guide
This page shows you how to install your 12-speed Di2 rear derailleur, set the B-screw, limits, and fine-tune the shifting using micro-adjust
Manuals & other documents
Firmware updates
Below is an overview of all known firmware updates for this component. The changelog texts are Shimano's, and quite often they're a bit cryptic - sorry!
4.2.3
■ ChangesSecurity performance for wireless communications between the shifter and rear derailleur has been improved.Click here to view FAQs for more information. https://bike.shimano.com/faq/DI20A#D-7030*The firmware for both the shifter and rear derailleur must be updated for proper operation of the Di2 system.■ OthersGeneral bug fixes.
4.2.1
Firmware released.
More images