**What di2 cord lengths do I need to buy? **I’m installing di2 on a 54cm 2018 Cervelo S5.
What components do I need for a fully functional di2 setup?
I have come into a set of shifters, a rear mech & front mech all di2. I have a charger.
I have no batteries, no cables and no junction boxes.
Help! Thank you in advance!
**What di2 cord lengths do I need to buy? **I’m installing di2 on a 54cm 2018 Cervelo S5.
What components do I need for a fully functional di2 setup?
I have come into a set of shifters, a rear mech & front mech all di2. I have a charger.
I have no batteries, no cables and no junction boxes.
Help! Thank you in advance!
You need a battery, Junction A, Junction B, wires and some of the proprietary Cervelo parts for using Di2 in place of mechanical shifting. I haven’t build up a late model S5 with Di2, but I think this clearly illustrates what you’ll need: https://www.cervelo.com/media/gene-cms/s/5/s5_disc_manual_v5.7_web_1_.pdf
You can consider adding in a Shimano BTLE D-Fly module in the handlebar inline with the EW-RS910 Junction A for using the Shimano e-tube app and/or communicating with a Garmin head unit. This setup also allows using the top brifters buttons to flip head unit screens (assuming newer DA or Ultegra models)
Awesome info. Thank you.
This is a 2018 (the last year before it became an integrated cockpit).
I’m thinking (hoping) there may not be need for proprietary parts.
Awesome info. Thank you.
This is a 2018 (the last year before it became an integrated cockpit).
I’m thinking (hoping) there may not be need for proprietary parts.
Sorry. A quick search didn’t turn up the 2018 manual. I have the prior Gen S5 to yours with Di2 installed. Your install will depend on what you have for bars and stem. I’m also not sure what was used for the Di2 battery mount for yours. You can see how it was handled in 2019 with the internal proprietary Cervelo downtube mount. This is used because the S5 seatpost is aero and narrow. I’m out of town or I could check one of mine to see how the internal battery might fit. Otherwise you’ll need some other mount option. The prior Gen S5 used the external battery mount on the NDS bottom side of BB and Chainstay. There were nutzerts installed there, but I’m guessing these were gone by 2018.
I still prefer using the ew-rs910 bar end junction a for a clean road bike install. I assume the Cervelo S5 aerobar allows running wires through the center of bar or aero front crossing. With this you just need an E-TUBE wire long enough to connect two brifters ports. You then need to connect one brifters to the junction A in the bar end. Then you can either run an E-TUBE wire from the second brifter port of the other junction to the frame downtube. Or run a slightly longer wire from the other junction A port to downtube. Same option here for placing the d-fly inline somewhere in the bar. Newer R5’s using the Cervelo bar and stem have a wire exit at back of bar clamp area that then runs through the stem and into the top tube behind the stem. If urs is similar you can do this and put the d-fly inline here as a junction b connnector. There is also a similarly shaped 2 port junction b that works the same way.
You’ll need a 4 port junction B in the BB area to link the E-TUBE wire from the bars, the FD E-TUBE wire, the RD E-TUBE wire and the battery E-TUBE wire. I usually wrap this junction in thin foam so it doesn’t rattle. It also helps to use small zip ties or Shimano similar clip on wire tie dampers to keep wires from rattling. If you can’t come up with Cervelo battery mount of some sort you can always use foam or bubble wrap and stuff it in downtube or seat tube assuming there is an access hole in bottom of BB. If there is hole there will be Cervelo rubber plug available to use in place of muechanical cable routing plug.
Hopefully I’m covering all here. I like to measure for wires then sketch up the layout before procuring what I need for the Di2 install.
Hopefully I’m covering all here. I like to measure for wires then sketch up the layout before procuring what I need for the Di2 install.
Yeah… sketching your wiring is definitely the way to go.
As for length, I tend to measure along the frame (using a piece of string for example) and then add some. The Shimano Way is:
Measure the length you need, then go the next size up and then add 50.
So if the measured distance is 280mm, the next size up is 300 and they’d recommend a 350mm wire.
Exceptions are usually the FD wire and seatpost battery wire (if your seatpost can be taken out AND the battery is installed in the seatpost) - you’ll want to be able to take out the entire seatpost with the battery still attached
For the front derailleur, make sure you get the wire length that’ll let you actually connect the FD to the junction B… sometimes the wires have to be routed around the bottom bracket or other frame material.
it’s usually OK to get longer wires rather than short ones… you can hide excess wire in the frame, but you can’t really make a short wire longer 
As Di2Terry mentioned, it’s generally better to go with wire lengths that are too long rather than ‘just right’. There are some limits to the maximum combinations of wire lengths, but even those are very generous.
How long your wires are depends somewhat on what junction box you use.
(Bar end 2 port junction box)
~250mm wire from junction box to shifter1 (i imagine this is the left shifter, but that’s preference)
~650mm wire from shifter1 to shifter2 (across the handlebars, need excess to adjust shifters)
~1250mm (maybe 1400mm) wire from shifter 2 to bottom bracket (through handlebar, along rear brake line, through downtube, out BB by 5-10cm. Connects to internal B-junction
~B-junction box
~500mm wire from B-junction to FD
~ 850mm wire from B-junction to RD
~ 850mm wire from B-Junction up through seat tube to battery
the Battery sits inside the seat tube (around the point of the FD). I typically wrap the ends of the battery with a bit of packing foam and electrical tape (like a barbell) just to reduce/prevent bouncing around. I also tape on an old brake cable to the battery with the end sitting just above the seat tube so I can easily fish out the battery if needed.
(If you go with a standard 3 port junction box)
~2x350-450mm wire from shifter to junction box
~1000mm wire from junction box to bottom bracket (along rear brake line, through downtube, out BB by 5-10cm. Connects to internal B-junction
~B-junction box
~500mm wire from B-junction to FD
~ 850mm wire from B-junction to RD
~ 850mm wire from B-Junction up through seat tube to battery
There are some limits to the maximum combinations of wire lengths, but even those are very generous.
hah, definitely!
I have built 8000 mm and 10.000 mm Di2 “circuits” (from battery to rear derailleurs) to test the maximum wire-chain length and both of these worked fine. I’ve posted some instagram stories/highlights on that for those that are interested: https://www.instagram.com/stories/highlights/17885136169700295/?hl=nl
(Shimano docs say 1400mm is the max for a single wire on a road bike though, but in reality this won’t be an issue)
Out of a lack of options, I have previously put 3x1400mm wires together in a circuit (downtube, RD, battery) and all worked fine despite the fact that shimano states that it’s beyond the maximum length combinations.
…but that’s still way less than what you’ve found. That’s impressive!
Beautiful! Thank you!
Beautiful! Thank you!
It looks like the internal battery mount is also used for your 2018 S5. Found a copy of the manual here: https://www.manualslib.com/manual/1513250/Cerv-Lo-S5.html?page=29
$25 at Excel Sports or My Bike Shop online.
This answers my long-unanswered question of what the heck those screws were for. Thank you!
Awesome info. Thank you.
This is a 2018 (the last year before it became an integrated cockpit).
I’m thinking (hoping) there may not be need for proprietary parts.
I have a 2016 S5, so basically the same as yours, with Di2.
The cable plug on the top tube will be different for Di2 - instead of the two port shift cable stop, you will have a rubber triangular piece with a hole in the middle for the Di2 wire.
The chainstay exit hole will have a different plug as well - it won’t be a cable stop plug, but a plug with a Di2 wire size hole in it.
The FD hole will need a Di2 exit plug as well, I do believe the regular Di2 cable plug will work but not 100% sure.
I think that’s it. You won’t need the cable guide under the BB, but the rubber port cover is the same for mechanical and Di2, I believe.