Shimano Nexus 7 hub cassette joint and lock ring

Shimano Nexus 7 Hub SG-7C18 Lock Ring Problem

I had a flat on my rear wheel. My bicycle is equipped with Shimano Nexus SG-7C18 7-speed coaster brake and in order to change a tube you need to remove both the chain and the internal Nexus 7 hub cassette joint.

Shimano Nexus 7 hub cassette joint and lock ring

Shimano Nexus 7 hub cassette joint (39) and lock ring (13)

That part seemed easy to do, but the trouble came when I tried to reinstall the Shimano Nexus 7 hub cassette joint with cable and lock ring. Even when hub twist shifter was set to speed 1 as advised and had the matching yellow arrows (shifter cassette joint) and dots (lock ring) properly positioned, lock ring wouldn’t lock by turning. It seemed as there wasn’t enough space between the ring and the cassette joint as the lock ring locks in grooves behind the casing.

After I took the bicycle to a mechanic, he told me he had a hard time locking the lock ring, too. His advise was to put shifter in position (speed) 1, put the cassette joint on the hub, use your fingers to open (tension) the cassette joint as wide as possible and this creates enough space for the lock ring to be locked. I hope I won’t have to repeat this procedure as it seems overly complicated. One would expect better from Shimano.

Complete list of Shimano Nexus 7 internal hub parts as well as installation instructions are available as PDF files directly from Shimano website.

  • I struggled just like you at first until I read the proper alignement sequence in the shimano tech doc:

  • Daniel

    I have tried to follow the manual you posted then but it didn’t work for me.

  • guyhofmann

    One must unleash the wire to be able to move the locker and the ring below (which is supposed to be locked !).
    It was not possible to properly fasten the locker until I unleashed the wired!
    Then it worked out just fine. – Thanks to Guilaume who provided the PDF-Link.
    guyhofmann (Germany

  • tom

    you can come to bikekitchen with things like this. We like to dismantle everything

  • D MM L

    Thanks for the posting here. The trick is that you need to release all the tension on the cable. And then the alignment is between the triangles and then the circle on the locking ring. Only after releasing all the tension on the cable was I able to get the whole piece to sit properly on the hub. The locking ring does not need any forcing and easily turns to lock position .

  • Thanks for the advice! I am now less eager to try it again myself, but rather will take this to a shop to be fixed :-)

    But maybe it can help someone.