Compact, reliable, and engineered to perfection, the Shimano SM-JC41 Junction B is the heart of internal Di2 electronic routing — quietly powering the seamless communication between your derailleurs, cockpit, and battery within your frame. As part of the Dura-Ace 9070 series, this 4-port junction acts as the central nervous system of your E-Tube Di2 setup, enabling precise, lightning-fast shifting in a clean, fully-integrated configuration.
Designed for internal frame placement, the SM-JC41 is strategically positioned to connect the Di2 wires coming from the front derailleur, rear derailleur, battery, and cockpit controls. Its low-profile and lightweight construction makes it ideal for sleek internal cable management, enhancing not only aerodynamics and aesthetics but also protection from external elements.
Built around Shimano’s E-Tube SD50 system, the SM-JC41 features four SD50 ports, allowing seamless plug-and-play integration with all compatible components. Installation is straightforward, with each port offering a secure, vibration-resistant connection. Whether you're setting up an endurance road machine, a performance gravel bike, or a high-end aero frame, this junction ensures your electronic drivetrain remains synchronized and dependable in every condition.
Key Features:
4-Port Design: Supports front & rear derailleur, battery, and cockpit interface connections.
Internal Mounting: Built-in style junction sits securely within the bike frame for clean, integrated routing.
E-Tube Compatibility: Designed exclusively for SD50 wiring, compatible with all E-Tube Di2 components using SD50 connectors.
Reliable Performance: Maintains crisp, uninterrupted signal transmission throughout your Di2 system.
Ultra-Lightweight: Weighs only 4.1 grams, preserving your bike's weight balance and performance.
Specifications:
• Model Number: SM-JC41
• Series: Dura-Ace 9070
• Weight: Approx. 4.1 g
• Type: Built-in internal junction
• Ports: 4x SD50 ports
• SD300 Compatibility: Not compatible (0 SD300 ports/connectors)
Ideal For:
High-performance road bikes using Shimano Di2 electronic shifting
Bikes requiring clean, internal routing of Di2 wiring
Riders looking for long-term reliability and plug-and-play simplicity
Custom builds and frame upgrades with internal Di2 architecture
Whether you're upgrading to Di2 or refining your bike’s cable layout, the Shimano SM-JC41 Junction B is the critical internal hub that keeps every shifting signal clear, fast, and reliable. A must-have for precision electronic drivetrains — trusted by elite mechanics and pro teams around the world.
