Shimano SM-JC41 built-in Junction-B for Di2

The SM-JC41 is the hub of an internally wired Di2 system. Four E-TUBE ports take the wires from the front derailleur, rear derailleur, cockpit and battery, and the whole unit lives inside the frame where nothing can snag it.

Highlights

  • Junction-B for Di2 systems
  • Four ports for EW-SD50 E-TUBE wires
  • Built-in type, housed inside the frame
  • Shimano quotes 4.1 g

Where it sits in the system

Junction-B is the distribution point. Everything downstream of the cockpit plugs into it, which is why it is the part you go looking for when a Di2 system stops responding on one derailleur. Keeping it inside the frame protects those connections from grit and water.

Compatibility and fit

For Shimano Di2 systems wired with EW-SD50 E-TUBE wires and routed internally. Your frame needs to have room to house the junction. If you are running external wiring, you need the external Junction-B instead. Ask us if you are not sure which your bike is set up for.

Shimano warrants this component against defects in materials and workmanship. Normal wear is excluded, which here means wear to the connector ports and port seals with repeated connection and disconnection, along with water ingress from a damaged or incorrectly seated connector, crash damage and damage from incorrect fitting.

Warranty claims and returns are handled by Tune Cycles. Contact us with your order number, send the part back to us, and we will assess it and lodge the claim with the distributor on your behalf. Please do not send the part to Shimano directly.

  • Shimano Di2 Junction-B
  • Built-in type for internal frame routing
  • Four ports
  • For EW-SD50 E-TUBE wires
  • Shimano quoted weight: 4.1 g
Part codeSM-JC41
FunctionJunction-B (Di2)
TypeBuilt-in
Ports4
Wire typeEW-SD50 E-TUBE
RoutingInternal
Quoted weight4.1 g
SKU SHM-ISMJC41
Barcode # 4524667827467
Brand Shimano
Shipping Weight 0.3000kg
Shipping Cubic 0.001000000m3
Unit Of Measure each

Must be installed and serviced by qualified bicycle mechanic