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Shimano Di2 E-Tube SM-JC40 External Junction Box

While many of today's framesets feature internally routed and integrated Di2 e-Tube wiring capability, the popularity of the most precise and reliable electronic shifting system is still a great upgrade for framesets without internal routing, and Shimano supports this with a variety of external set-up specific parts. The Shimano e-Tube Di2 SM-JC40 External Junction Box mounts underneath the bottom bracket, where a derailleur cable guide is usually located. The included screw (2 length options) threads into the hole that is normally used for the cable guide mounting screw. It becomes the central connector for Di2 e-Tube systems. Wires from the front and rear derailleurs, cockpit area, and battery all plug into the 4-port SM-JC40 junction, which integrates the inputs for full connectivity.


  • 4-port junction box for externally wired Di2 e-Tube set-ups; integrates the ported wires
  • Can connect e-Tube wires from: front and rear Di2 derailleurs, cockpit junction, battery
  • Attaches to bottom bracket cable guide mount
  • Includes prepped mounting screws; in 2 lengths for best fit into threaded frame insert
  • Composite material with stainless steel sleeve washer for screw
  • Color: Black
  • Weight: 10 grams
  • Shimano part # ISMJC40
Item is in stock