Shimano
Di2 4-Port Junction Box
Best central hub for cyclists building a clean electronic shifting system.
The Shimano Di2 4-Port Junction Box (EW-JC304) serves as the central hub for your electronic shifting system. It efficiently manages connections, providing four ports to link your shifters, derailleurs, and other Di2 components. This essential piece ensures organized cable routing and seamless communication within your drivetrain, contributing to a clean cockpit and reliable, high-performance shifting. Keep your electronic setup functioning optimally with this key component.
$33.99
Owner Satisfaction
4.6
/ 5
Category Rank
359
/ 2100
#359 in Components
Price vs Category Average
-67%
Below average
Model Number
304
/ EW-JC
Who it's for
- Mechanics performing routine maintenance and system diagnostics
- Cyclists building complex setups with multiple satellite shifters
- Minimalists seeking a clean and professional cockpit aesthetic
Who should skip it
- Riders navigating rough terrain or harsh weather conditions
- Owners upgrading to the latest 12-speed wireless groupsets
- Budget-conscious cyclists maintaining older electronic shifting systems
Performance breakdown
Signal Reliability
Ensures consistent, lag-free communication across your entire electronic drivetrain.
Cable Management
Simplifies complex routing for a clean, professional cockpit aesthetic.
Installation Ease
Plug-and-play design makes integrating multiple components straightforward and intuitive.
Build Durability
Rugged construction withstands the vibrations and elements of daily riding.
System Versatility
Four ports provide ample flexibility for custom shifter and accessory configurations.
Component Integration
Seamlessly bridges the gap between derailleurs and shifters for optimal performance.
Key Specs
Model Number
EW-JC304
Port Count
4
Brand
Shimano
Category
Components
Features
- Manages Di2 electronic shifting connections
- Four dedicated connection ports
- Organizes cable routing
- Ensures system functionality
- Facilitates smooth shifting
- Central communication point
What customers say
Consumers view the Shimano Di2 Junction Box as an exceptionally reliable core component of the electronic shifting ecosystem. Its primary strength is its dependable, set it and forget it functionality, which underpins the entire system's precise performance. Users value how seamlessly this hub connects all shifting elements and serves as the essential charging and diagnostic port without issue. While it is a functional piece, its consistent, flawless operation is paramount to the celebrated effortless shifting experience. Cyclists appreciate the durability and peace of mind offered by this central hub. Its high value is accepted as integral to investing in a premium electronic groupset, making its dependable performance a cornerstone of overall Di2 satisfaction.
Know before you buy
The EW-JC304 acts as a central hub for your Di2 electronic shifting system. It provides four connection ports to link your shifters, derailleurs, and battery, ensuring reliable communication and power distribution throughout the drivetrain.
The EW-JC304 is specifically designed for use with newer 12-speed Di2 systems that utilize the updated EW-SD300 wire standard. It is not compatible with older 11-speed systems that use the thicker EW-SD50 cables.
Because it is a compact, internal-style component, it is typically hidden inside the frame or cockpit area to keep your cable routing clean. Its small form factor allows for discreet placement while maintaining easy access to your connections.
You should use the Shimano TL-EW300 plug tool to safely insert and remove the wires. This prevents damage to the delicate pins inside the ports and ensures a secure, weather-resistant connection.
Yes, the four ports provide the flexibility to integrate additional components like climbing or sprint shifters. As long as you have an available port, you can expand your system's functionality.
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$34