I have DI2 installed on the V20 and the S40.
Overall I like it. Shifting is great.
My only complaint is that you cannot shift if the battery goes dead.
And I have had the battery go dead 4 times now overnight while not even using it (and not always on the same bike).
I’m pretty sure it was caused by the wireless (BLE / ANT+) transmitter not turning itself off.
It hasn’t happened since I took it off the bike (I was using the SC-MT800 which was nice because it displays the gear you are in).
On the S40:
Rear derailleur: RD-R8050. Spec says max 32-tooth cassette but I’m using an 11-42 cassette with the B-screw almost all the way in.
Shifting is kind of clunky but I think that is true for almost all derailleurs using a wide-range cassette.
Shimano has a new RD with a friction clutch to reduce chain slap. I haven’t seen one but it might be worth looking in to.
Front derailleur: FD-R8050 braze-on. It shifts well with round chainrings (52/36) but I haven’t been able to get it to shift well with q-rings.
Battery:
I installed the BT-DN110 seat post battery inside the slider (wrapped in bubble tape so it won’t rattle).
I use two of the Shimano SW-R600 remote shift switches instead of buying the rather expensive Shimano brifters.
The remote shift switches work well but I would much rather have something like the SRAM Blip switches (much smaller and can be installed under the bar tape).
Wiring:
I wanted all the wiring to be internal, so I drilled two small holes in the chainstay (just large enough for the wire to fit but much smaller than the connector). Then I cut the wire, fed it through the chainstay and soldered it back together.
You could easily install it without drilling holes and fishing the wire through the chainstay.
There is a drain hole at the bottom of the boom (just behind the bottom bracket shell). Wiring from the FD and RD can feed into the boom / slider here.
Wiring from the shifters and the A-Junction (control box) on the handlebar can be fed into the slider without drilling holes by feeding the wires between the handlebar clamps. Then all the connections are made in the slider: FD, RD and battery -> junction box, junction box -> A-junction and shifters on the handlebar.
