External Junction B (SM-JC40)

The junction box SM-JC40 is used externally, when internal cable routing or an internal junction box (SM-JC41) is not possible. It is usually placed underneath the bottom bracket, fixed to the frame using a screw.

External Junction Box B - SM-JC40

Details & specifications

Shimano model codeSM-JC40
Shimano model nameJunction B (external)
Weight8 g
SeriesUltegra 6770, Ultegra 6780, Ultegra R8000, DURA-ACE 9070, DURA-ACE R9150
Downloads Junction B Manual
View on Amazon (new tab)  |  eBay (new tab) Chain Reaction Cycles (new tab)

Shopping links

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The SM-JC40 is installed underneath the bike, below the bottom-bracket. It attaches using a mounting bolt and takes up to four e-tube wires.

SM-JC40 installation SM-JC40 wire installation