External versus internal routing Di2 Trek Emonda S4

[JMeinholdt]

Got a good deal on Force AXS for my primary bike and part of the deal was giving my current Ultegra Di2 to my wife for her bike.

She has a 2016 Trek Emonda S4 WSD. Completely external routing. My set up has the DN110 battery. My question is, would it be possible to install the battery internal (she has a compatible seatpost)? My thought would be to install the battery internal and enlarge the drain hole just enough to pass the wire through to an under BB style junction box.

Am I crazy in thinking this may be possible? Is it an open BB shell?

Other thoughts?

[JMeinholdt]

Anyone? To add to it, I measured the drain hole. It's about 3.8mm whereas the Di2 connector is about 4.5mm. So we're not talking a huge enlargement...

There's also the possibility of cutting and splicing, but I'm not too keen on that idea. The wire itself would easily clear without drilling. I really don't think an additional 0.7mm is going to make a difference. It's not like they mold the drain hole in the carbon. If anything, they simply reinforce the area around the intended hole which should extend enough to clear the additional area.

And if I can't pass the cable around the BB shell, it doesn't matter anyway. I don't plan on checking that myself until I tear it down to do the swap.

Thanks.

[RECAR77]

does the seatpost have the proper internal diameter for the battery? you also have to unistall the bb and might need a new one. the bb shell might also be closed/obstructed on the inside.

I would use a PRO vibe di2, korjak di2 or tharsis stem and use the "pro gap cap expander di2" to store the internal battery in the steerer tube (assuming it is long enough) and with the rest go full external. that approach would be the least annoying and time consuming in my opinion.

but yeah, I'd agree that making the hole larger wouldn't be an issue if you want to go that way.

how do you plan to secure the externally routed di2 wires?

[IvanZg]

I'd take 5mm drill and enlarge that hole without any second thoughts. Wire should go fairly easily round that plastic sleeve as its diameter is slightly larger than crank arm spindle.
Do you plan to drill exit holes on top/bottom tube to connect with shifters?

[FIJIGabe]

Honestly, I would look at getting an SL frame in that size, and transferring everything over. I was able to score an SLR frame for under $500, and the only difference between the WSD and "regular" frames are the contact points, not the geometry. I would just transfer everything over and run Di2 internally.

[JMeinholdt]

does the seatpost have the proper internal diameter for the battery? you also have to unistall the bb and might need a new one. the bb shell might also be closed/obstructed on the inside.

I would use a PRO vibe di2, korjak di2 or tharsis stem and use the "pro gap cap expander di2" to store the internal battery in the steerer tube (assuming it is long enough) and with the rest go full external. that approach would be the least annoying and time consuming in my opinion.

but yeah, I'd agree that making the hole larger wouldn't be an issue if you want to go that way.

how do you plan to secure the externally routed di2 wires?

She has a Zipp Di2 ready seat post. I'd never heard of storing the battery in the steerer. That may be an option. She does have a 44cm emonda with I think around a 100mm HT. The steerer is uncut though, so it may just be enough. My real concern is that the BB shell obstructs the path for cable if we did the seat post install. My plan for the rest is to do a stem mounted junction A, use the Di2 specific adhesive along the bottom of the down tube, bottom bracket mounted B junction, and the Di2 adhesive along the chainstay.

I'd take 5mm drill and enlarge that hole without any second thoughts. Wire should go fairly easily round that plastic sleeve as its diameter is slightly larger than crank arm spindle.
Do you plan to drill exit holes on top/bottom tube to connect with shifters?

I'm sure the wire would pass around the BB itself, but I just don't know if it has a closed BB shell bonded into place, and if so, if it would obstruct the cable. I haven't torn it down yet.

I will not be drilling any other holes in the frame. She's ok with the wire along the downtube.

Honestly, I would look at getting an SL frame in that size, and transferring everything over. I was able to score an SLR frame for under $500, and the only difference between the WSD and "regular" frames are the contact points, not the geometry. I would just transfer everything over and run Di2 internally.

Trying to do this as cheap as possible and swapping a frame isn't ideal. Plus, we just picked this one up for her a few months ago and she digs the color scheme.

Honestly, the external isn't so bad provided we have a solution for the battery.

[IvanZg]

Is there a screw holding that black plastic piece on the bb shell? The hole might be big enough for the connector. I do not know what sort of BB that is, but if it is a 2 piece design you might just drill a straight hole through that screw/drain hole and the other side of bb sleeve if there is one.

[JMeinholdt]

Is there a screw holding that black plastic piece on the bb shell? The hole might be big enough for the connector. I do not know what sort of BB that is, but if it is a 2 piece design you might just drill a straight hole through that screw/drain hole and the other side of bb sleeve if there is one.

There is, but there's where I planned to mount the B junction. I'll pull the seat post tonight and look down toward the BB area to get a better idea of where I stand on this project.

[RECAR77]

She has a Zipp Di2 ready seat post. I'd never heard of storing the battery in the steerer. That may be an option. She does have a 44cm emonda with I think around a 100mm HT. The steerer is uncut though, so it may just be enough. My real concern is that the BB shell obstructs the path for cable if we did the seat post install.

di2 battery is ~155mm I think and the special expander needs around 1.5-2cm more (I shold have one of those expanders in the shop so I could measure it tomorrow to be sure). you could just try dropping the battery into the steerer (connector side first) and see how much room you have left to the top of the steerer. you could also go the super budget/rustic way and just get the special expander without the stem and drill a 5mm hole into the topcap to get the cable out.

My plan for the rest is to do a stem mounted junction A, use the Di2 specific adhesive along the bottom of the down tube, bottom bracket mounted B junction, and the Di2 adhesive along the chainstay.

since you have all external cable routing there is a way that might look cleaner for longer (tape wrinkles and peels off over time and leaves residue) and is easier to remove. you can hang a roadbike brake or normal shift cable nipple into the downtube cablestop, route it like normal towards the rear derailleur and secure it in the chainstay cable stop with a cable nipple. before you secure it you take some heatshrink tubing and route the brake/shift cable and the di2 cable through it. after securing it you take a heat gun and shrink the tubing.

[JMeinholdt]

Double checked the clearance around the BB for the cable. It is a closed BB shell, but there's plenty of clearance as the drainhole is slightly to the front of the BB shell. Looks like with slight drain hole enlargement, I'll be able to run the battery in the seatpost. Honestly, I won't even need to pull the BB.

It'll be a few weeks as I've got a lot of parts to come in, then I have tear down and install AXS on my bike, then I'll do the Di2 install on hers. I'll update this thread when I start it.

Thanks all.

[JMeinholdt]

Got this installed, in case anyone is interested in this. I did drill out the drain hole and installed the battery/wifi module in the seat tube. All said, drilling took barely more than the paint off the hole. Not concerned about structural integrity at all.

In addition, the plastic insert that routes the FD cable through was able to be removed to route the Di2 cable. I used the Shimano cable adhesive, which I'm not so sure about the strength of it, but so far has held out.

Kind of a nest of wires at the BB, but it could be a lot worse. Overall, for my first external Di2 installation, I'm pretty pleased.

Unfortunately, she has white cables. I may get some white heat shrink tubing to clean this up a bit.


BB junction box.


BB junction box from underneath. You can see the drain hole here.


FD cable.


RD cable.

[TheRich]

White electrical tape would be easier.

I wrapped my Di2/brake hoses in electrical tape and you can't tell the difference unless you really look.

Looks good though, hope she's happy with it.

[JMeinholdt]

White electrical tape would be easier.

I wrapped my Di2/brake hoses in electrical tape and you can't tell the difference unless you really look.

Looks good though, hope she's happy with it.

Good point about electrical tape. I may try that just to see how it looks.

And she does like Di2. She has small hands so the lever throws were a bit hard for her to manage. I programmed it with full synchro and a SRAM style shift pattern so all she does is do right button faster and left button slower.

She's definitely the slowest person the group ride with Di2, but now she's more likely to be on the group ride at all, so that's a win for me.

[fruitfly]

Thanks to all for the helpful replies. I contacted the builder, who agreed that their records had the frame down as di2, and they just forgot to drill the holes during the build. They will send me a shipping label so I can return the frame to the shop where they will drill the holes. So mildly tedious, but will produce a professional outcome.

Hugh

[PSM]

Yellow electrical tape?

I think your wife deserve a new frame.