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  • Shimano E-Tube Di2 Junction Box
  • Shimano E-Tube Di2 Junction Box
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  • Shimano -
ShimanoE-Tube Di2 Junction Box
Sale 26% Off$20.71 - $26.03

Item # SHI0394

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  • One Color, External/SM-JC40 ($26.03)
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Item # SHI0394
Description

Where the wires converge.

The E-Tube Di2 Junction Box is what is referred to as the B Junction. This is the point in the wiring system where all the component pieces converge. It's a crucial item along with the five required wire sections to operate your Ultegra 6770, Ultegra 6870, or Dura-Ace 9070 Di2 shift system.

The E-Tube Di2 Junction Box is available in two configurations—Internal (SM-JC41) and External (SM-JC40). The Internal style is designed to be located inside the bike frame (usually inside the down tube, tucked in from a hollow bottom bracket shell). The External version is designed to be fixed on the outside of the bottom bracket shell, usually fastened to the cable guide.

  • Connects Di2 cycling component and battery wires
  • Available in external or internal configurations
  • Shimano's Di2 is the most popular electronic drivetrain in the pro ranks
Tech SpecsSize
Tech Specs
Crankset Compatibility
2 x 10
Compatible Components
Shimano Ultegra Di2
Recommended Use
ditching your mechanical tethers
Manufacturer Warranty
2 years
Size

Shimano

Di2 Reference Guide
Battery and Wires: Our Shimano Di2 packages are built for three standard configurations based on battery location and wire routing. First, you'll need to determine if your frame uses an internal or external battery mount, and whether the routing is either internal or external. Below is a guide for which battery, charger, mount, and junction boxes are required for your configuration.
Battery & Wire ConfigurationsBatteryBattery ChargerBattery MountJunction AJunction B

External Battery

with External Routing

SM-BTR1

SM-BCR1

SM-BMR2

SM-EW90 A/B 3/5 port

SM-JC40

External Battery

with Internal Routing

SM-BTR1

SM-BCR1

SM-BMR2

SM-EW90 A/B 3/5 port

SM-JC41

Internal Battery

with Internal Routing

SM-BTR2

SM-BCR2

 

SM-EW90 A/B 3/5 port

SM-JC41

Battery Mounts: The SM-BMR2 battery mount is available in three configurations -- Long External, Short External, and Long Internal. Both Long versions are to be mounted using the bottle cage mounts, while the Short version is designed for Di2-specific frames with either a chainstay or down tube mounting location.

Junctions: There are two junctions needed for completing your Di2 build -- A and B. Junction A, SM-EW90, is located at the handlebars and available in both three- and five-port options. The three-port option is intended for standard shifting with a left and right hand shifter. If you have the intention of using Shimano's satellite sprint shifters, or a combination of time trial shifters and shifter/brake levers, the five-port junction box will be the necessary selection.

Depending on your frame specification, Junction B (SM-JC40 or SM-JC41) is located either internally or externally at the bottom bracket area. Accordingly, SM-JC41 is designed for frames with internal wire routing, while SM-JC40 is intended for external wiring options.

E-Tube Wires: For your convenience, we've created wire packages for your Di2 build kit in the sizes Small, Medium, and Large. Below, you'll find which wire lengths are included in each kit. Additionally, we've recommended a kit size based on your frame size.
E-Tube Wire Length ChartSML
Down Tube Wire

700mm

750mm

950mm

Front Derailleur Wire

300mm

350mm

400mm

Rear Derailleur Wire

500mm

550mm

600mm

Battery Wire

300mm

350mm

400mm

Note: E-Tube Wire Length Suggestions are an approximation.
E-Tube Wire Frame Size Guide

S

M

L

Frame Size 47 - 52cm 53 - 56cm 57cm+
Note:
This reference is meant to be used as a guide for creating a Shimano Di2 drivetrain package. For further assistance please feel free to give us a call.

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Works well.

  • Familiarity: I've put it through the wringer

Works great, make sure to plug any unused ports (like in 1x setups) with the shimano di2 port plugs, or else water will get in and short it out.

Avg. ride time: 2h 29m per week
  • Average ride time is based on Strava activity over the last 3 months. Give your reviews credibility by connecting your account.

Gotta Have It

  • Familiarity: I've put it through the wringer

It's a necessity!