TiHabanero

I have need to modify a carbon frame made with internally routed hydro brakes and Di2 wires to accept a cable operated rear derailleur. Where the rear brake hose enters the down tube there is a slot for a Di2 wire alongside it. There is no separation between the brake hose hole and Di2 wire slot as they share the same opening in the frame. I think grinding this slot into a hole for to run rear der. housing will not compromise the frame at this location since the hole and slot are together in the opening. I am unable to post a picture at this time. The frame is a Specialized Roubaix Sworks with a single entry point on the down tube.

cxwrench

So you're thinking of using something like a Dremel to make that opening a little bigger to get the shift housing in w/ the brake hose? Then run full length housing and exit out the hole at the end of the chainstay? I've modified a couple of Shivs for a guy on the Specialized Master Team w/ the blessing of they guy who knows that stuff at Morgan Hill.
I honestly can't see any problems w/ this. Lemme know if you have any questions.

Iride01 

I think internally routed cables are more tricky to keep them moving easily enough to shift reliably and smoothly in every frame. That's probably why they have always been a niche group of bikes that had them.

Hydraulic brake hoses and wires for shifters made this issue much less a problem and that is probably why we are seeing more and more bikes with almost fully internal routings. But they are hydraulic and electronic shifting, not the old cable pulled stuff...... in most cases.

Andrew R Stewart 

The only issues I foresee with this is the voiding of any warranty and the resale value loss of a home modded frame. One would have to be pretty oblivious to mechanical common sense to do so much modding as to risk structural integrity. Andy

sch

Might be worth checking with any local Specialized dealers and/or Specialized website for adapters for the entry
area designed for wire pull RD instead of Di2 RD. Seems likely Specialized was aware not every buyer would
want Di2 and make provision for an adapter.

TiHabanero

I know the area around the existing opening is reinforced from the factory. Of course Specialized did not agree with doing the mod as they have a liability position, however the frame is second hand has no warranty as it sits. Think of a slot about 1/2 inch long that connects to a round opening so the thing in whole looks like a sucker on a stick. All that needs to be done is modify a portion of the slot to allow der housing to pass through next to the hole for the brake hose. I don't see an issue and am certain it has been done before.

cxwrench, I appreciate the input, as well as others who have opined. The real challenge is routing a front der cable. I will likely have to run it outside the down tube, and if that is the case, then I will run both der cables outside the tube. Trying to convince the guy to go 1x so he can have the clean look he desires. FWIW, internal routing is as dumb an idea the industry has ever had.

Iride01 

A little more than a year ago I might have agreed with you.

Since getting my Tarmac which has most of the brake lines and shift wires internal, I've found I clean my bike more. Partly because it's so much easier without the cables running along the top tube, down tube and chain stay.

Steve B.

My experience installing Di2 XT on a mt. bike that had internal routing mechanical rear shifting, was the E-Tube connector is larger than mechanical housing. Thus I would be surprised you would have to enlarge an opening already designed to accept passage of en e-tube connector. Have you tried running mechanical housing yet ?. Might fit.

As well if you do not have appropriate housing stops, just run full length housing from the shorter to the derailer. A lot of mt. bikes have this, use good quality housing and shift cable.

TerryDi2C

Yeah... the connector itself is ~5mm (diameter).