Shimano GRX Di2 RD-RX825 rear derailleur

The new GRX RD-RX825 Di2 rear derailleur with wireless interface and charging port. The Di2 platform is used in Shimano’s electronic 12-speed shifting components, where it ensures the world’s fastest and most reliable wireless shifting. Designed for 2x12-speed drivetrains with a maximum cassette size of 36 teeth

Shimano GRX DI2 RD RX825 Rear Derailleur Technical Specifications:

• Wide Link Design: the wider outer parallelogram increases stiffness
• Cold-forged aluminium
• 12-speed compatible
• Ball-bearing friction pulleys
• Smallest sprocket to be shifted, rear 11 teeth, maximum 11 teeth
• Largest sprocket to be shifted, rear 36 teeth, minimum 34 teeth
• Total capacity: 40 teeth
• Compatible with Shimano 12-speed Di2 shift levers
• Cable connection EW-300
• Weight 262 grams (manufacturer’s specification)

Shimano GXR Di2 12-speed

In the brand-new Di2 version, the 2x12-speed GRX RX825 combines SHIMANO’s unique expertise in electronic shifting systems with optimised gear ratios for a wide variety of gravel riding scenarios – from leisurely tours and races to multi-day adventure trips. The new Di2 groupset features redesigned DUAL CONTROL shift/brake levers for optimum comfort and control, a SHADOW RD+ rear derailleur for reliable chain management, and a gravel-optimised front derailleur for precise shifts from the large to the small chainring and vice versa. Designed with gravel riders in mind who set off on a whim, enjoy venturing down unknown paths or throw themselves into adventures with an uncertain outcome, SHIMANO guarantees precise, trouble-free performance in every conceivable condition with the GRX Di2.

Shimano Di2 12-speed

The new Di2 platform for 12-speed components requires no cable connection to the rear derailleur and front derailleur. The Di2 DualControl 12-speed shift/brake levers have the necessary wireless module integrated. Power is supplied by CR1632 batteries, which have a service life of up to 2 years. The Di2 12-speed rear derailleur, with its additional wireless unit, acts as a receiver and distributor of shift signals and is connected to the battery and front derailleur for power supply and shift command transmission. Additional wireless components, including those from third-party manufacturers, can also be paired with the rear derailleur.

Shimano GRX RD RX825 Di2 Rear Derailleur

The new ULTEGRA rear derailleur is the centrepiece of the new Di2 components. It provides the wireless functionality and connection to external components, and also includes the charging port, replacing the previous SM-BCR2 charger. Furthermore, the rear derailleur houses the transmitter for wireless communication with the STI shifters and other external devices, including those from third-party manufacturers. It also features the status LED and the adjustment button, which is used, for example, to switch between Synchro-Shift modes, meaning that the previous Junction A port, SM-RS910, is no longer required.

Synchro-Shift technology

Synchro-Shift technology greatly simplifies shifting and significantly reduces the number of decision-making processes that take place whilst riding. Particularly in crucial race situations or when riding at full throttle, riders often have to navigate a multitude of decision-making processes alongside the physical strain, which are frequently disrupted and lead to wrong decisions. The fewer decisions there are to make, the better the decisions will be and the more attention can be focused on the race. This is precisely what Shimano Synchro-Shift technology enables, always selecting the optimal next-higher or next-lower gear combination, regardless of whether this requires shifting at the rear derailleur and/or the front derailleur.

Shimano Synchro-Shift functions

• Full Synchro-Shift: The front derailleur reacts to the gear changes the rider makes on the rear derailleur. Essentially, this means that only one shifter with two buttons is needed to operate both the rear and front derailleurs.
• Semi Synchro-Shift: The rear derailleur responds to the gear changes the rider makes on the front derailleur. The rear derailleur automatically performs the necessary compensatory shifts for small changes in cadence when shifting up or down on the front derailleur.

Shimano 12-speed Di2 installation:

Shift commands are transmitted wirelessly from the shift levers to the rear derailleur. Only the rear derailleur and front derailleur are connected to the battery via cables. This ensures a clean look and significantly reduces the installation effort. The shift levers are powered by CR1632 batteries. The shift levers feature an additional cable connection, which allows for the connection of auxiliary switches. Traditional cabling from the shift levers to the battery is also possible. The new battery has three slots.

Herstellerinformation: SHIMANO INC., 3-77 Oimatsu-cho, Sakai-ku, Sakai-shi, Osaka 590-8577, Japan, www.shimano.com | EU contact: Shimano Europe BV, High Tech Campus 92, 5656 AG Eindhoven, The Netherlands, www.shimano.com