Di2
 

Hi all
I am thinking of going with electronic shifting for the rear.
I would like to use the brakes and levers I already have.
So my question is can I use shift buttons only to control the derailleur and not install or buy the sti units.
Do I just need the buttons, junction box, associated cables and batterys.
Cheers

I'm not sure how well that will work. Di2 automatically trims the front derailleur when you shift the rear derailleur.

I don't really mind about the fd.
I friction shift the front now anyway and can live without di2 for the front.
I am really only want to shift the rear with buttons alone.
Cheers

It's a package deal. You need the shifters as well as the derailleur. Lots of reasons.

Damn. Ah well I shall have to do without it.
Cheers

So actually you could potentially build a Di2 bike without using the STI levers and with a different front derailleur but honestly why? The Di2 STI levers feel fantastic and the ability to have brake levers again is fantastic. Unfortunately with the Shimano system they use the brake lever to shift as well and that doesn't jive with me.

I would rather just do the complete system rather than bodging around with some really odd set up unless you happened to be a special needs case like missing limbs or something. I get you are attempting to save a little money but honestly it isn't worth it. If you really wanted it just do the whole gruppo and keep in mind mountain and road Di2 derailleurs are not compatible as far as I know, yet. You can use mountain derailleurs with road shifters you just can't mix derailleurs.

Well, the system sends a signal to the (non-existent) front derailer to trim. Doubt there’s any feedback loop telling the system the derailer did nothing.

I’m thinking the OP could get away with this as it’s essentially a system used in Tri bikes, that do not use brake/shift levers, only 2-3 buttons.

At the very least you will need:

• one derailleur
• one junction A
• a couple of EW-SD50 electric wires (max length 1400mm for a road bike/mtb)
• some kind of shifter (EXCEPT SW-R610, this will only work if you plug it into a port on an STI)
• a battery

I agree with veganbikes though,.. I too would rather build a complete bike and use the Di2 STI levers.

Thanks I will have a look at this and see if it suits.

I used an SW 600 remote shifter ( https://www.amazon.com/SHIMANO-SW-R6.../dp/B07CSKJNV2 )
with an indicating junction A (ie it reads out the cog position of both or either the FD and RD and gives state of battery charge)
along with the cables, a battery and a 6770 RD on my long wheel base recumbent without any problems. So yes the OP CAN
get by without brifters. FWIW the SW 600 works with 6870 and 8070 series Di2 RD as well, it is not just for 10spd RD. As best
I can tell, the SW 600 is for RD only, ie it doesn't have the codes for FD shifting but "may" be reprogrammable with Shimano
software. But as supplied it replaces the right brifter as the controlling device for the RD.

You don't need brifter shifters if you use the SW-600, I have a bike set up that way. You need the latest battery, the charge unit a couple of wires and junction box and DR. You will also need a Windows computer to set up the shifting if you use a front and rear derailleur, as of a couple months ago Shimano had not fixed their apple app, check their web site

Thanks to everybody
I am getting closer to a solution.