I don't know exactly what you'd need for wiring, but I have a new-i-box set of 6870 shifters I'll sell cheap. PM me if interested.

What you don't need: Chainset, cassette, chain brakes

What you don't need but may want to consider: brake levers

What you do need: Mechs, shifters, junction box, cables, battery.

The biggest advantage of going electronic on a TT bike is shifting from the base bar but this is not strictly necessary and it is also an expensive upgrade. You can hack something together for cheaper using blips but that depends on your skill set.

Something like this is the easiest option to get you there but its probably not the cheapest option: https://www.vanillabikes.com/...24wGKCEaAsZiEALw_wcB

do you know if I were to get the 5 port junction would it work with just the extension shifter until a had more funds to add the brake/basebar shifter?

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2019 T-Rex Tri Series

This
https://www.ebay.com/...5:g:lmoAAOSw9hRa2~-o

I offered $850 and they accepted. They will send you a form to fill out asking what specific pieces you want. You will have to pay extra for the brake levers with shifters. I ended up doing the full install for about $1,000. You may need an extra etube or two depending on where you are mounting junction boxes.

Michael - sent you a PM. I'm actually selling a 6870 Di2 TT group off of my Shiv.

Read this post as most of it will apply to you on how to plan your upgrade: https://forum.slowtwitch.com/forum/?post=6572184

It helped me and serves as a very good guildeline on what is needed to get a Di2 system up and running on your own. I ended up upgrading both my road bike and Tri bike to Di2 (because I got issues with wanting to buy stuff). This year I've got major home renovations/repairs to pay for so no bike stuff (except I should replace my chains and maybe a cassette also).

Also add to the list a battery charger. They are a separate item/costs (doesn't matter which battery you get external or internal...it's extra). My take is don't buy wires until you know where your battery is going to be located. That will dictate lengths of everything and how many additional Junction "B's" you'll need (if any).

Yes. No problem leaving ports open on any Di2 junction box. I typically use the e-tube port plug for unused ports as insurance against moisture issues, it even without the plug I doubt it would cause a problem.