Di2 Upgrade

leejhayward Posts: 3
edited April 2019 in Workshop
Hello all,

I’m currently putting together a DI2 upgrade for my Giant TCR Advance Pro 2 – 2017. It is DI2 ready, but I am not quite :D
I’m intending to go with the EW-RS910 as my ‘junction box’ at the front end, so after drilling the bars I intend to wire; junction box to shifter (R), shifter (R) to shifter (L) and then shifter (L) to Junction Box B around the bottom bracket which will then connect Front & Rear Derailleur and the battery.

The question here is what routing path should I take? On the factory fitted DI2 TCRs, I can see that one of the cables enters the top tube. Shimano advise going into the down tube with Junction Box B and then back up to the battery in the seat post. I guess it is possible that on the TCR the cable comes in at the top tube, comes forward and then down into the down tube.

Giant seem to do a seat post mounting adapter for the oval shaped TCR seat post so I’ll be fitting one of these as well:


So questions, obviously I will remove the existing mechanical cables, I presume I will also remove the internal cables guides as well? Are these easy to refit, if for some reason I wish to refit the mechanical gearing?

I’m also intending to go to a 11/32 on the back from my current 11/28. I have a semi compact on the front (52/36) so I am getting the Medium cage RD, but I was wondering if I’ll need to swap the chain out for a slightly longer one?

I’ve asked a giant spares website for guidance on the grommets for the frame once the old mechanical gear is out of the way. As far as I can tell, I’ll need one for the old mechanical exit point at the back of the bottom bracket for the FD, a new grommet for the rear of the chain stay to accommodate the DI2 wire as opposed to mechanical cable and then one up front in the head tube to plug the old mechanical entry point?

Many Thanks,


  • The cable does go forward as you described if you enter on the top tube. Thats how I wired mine and I think it looks cleaner than going in the headtube where youll currently have mechanical cables, but you could route it through that if you wanted. If you dont use it though you can get the blanking piece for that:

    https://www.giantbikespares.com/Giant-F ... il/3-42610

    You want one of these for the chainstay as you noted:
    https://www.giantbikespares.com/Giant-F ... il/3-42609

    You probably want this type for entry to the frame (if going top tube entry) and for front mech:
    https://www.giantbikespares.com/Giant-D ... il/3-42883

    There is a small piece toothat goes in the hole where the mechanical wire would run from the BB to the front mech but cant find it listed right now.
  • Brilliant thanks, I hadn't spotted the Headtube plug previously, that looks just the job. With the large box section downtube on the TCR it should give plenty of room for the junction box. Did you find a particularly good way of preventing the junction box from rattling? I've seen cable ties used and that'll probably be the way I go.

    Also, I presume the internal cable guides can be removed when I take out the mechanical cables?

  • Ive never had a problem with junction box rattle and Ive had di2 for years now on various bikes. You can put the cable ties on the wires which is supposed to help but Ive stripped bikes before and found them not in place and hadnt noticed.

    I removed the internal cables guides. I dont think youll actually have a choice anyway but cant remember.
  • rafletcher
    rafletcher Posts: 1,235
    I loosely wrapped my JB2 in a few layers of thin bubblewrap. Never had a problem with it rattling. Likewise I've never heard any of the wires rattling either, it's always the internally run rear brake outer that slaps about in rough conditions.