Drilling one of two holes into a P4. Which should I drill?
 

I am installing Di2 on a 2011 P4. I have to make a hole from the bottom of the bike under the bottom bracket into the frame of the bike to access the seat post. One way or another I am drilling the hole tomorrow night. But I can not decide between:


1) Drilling up through the bottom bracket sleeve and then through the other side of the bottom bracket.
2) Drill a hole in front of the bottom bracket and having the cable go around the bottom bracket. This is my preferred approach but could it be solid around the BB and therefore not possible to route a cable? Also why have others not taken this approach and instead gone through the BB shell?


Like to hear thoughts on which approach.

I appreciate any feedback but I have already decided the following:

1) Do not care that it will void the warranty
2) I only want internal and not interested in external
3) Location of the battery I am only considering in seat post
4) Only interested in doing this myself. Not interested in sending off to a place or having local Cervelo LBS do the work. I really enjoy these types of projects and willing to accept if it turns out to be a disaster

Here are the pics. In the picture I need to get a cable from the bottom up to where you see the words "Curved Cutout Construction". You can see there is not much room in the frame above the bottom bracket shell. So looking at a cable going in front of the BB or to the left in the picture and then up. Basic question is it hollow above the BB. I am comfortable that if I can get by the BB I can fish the cable up.

If drill through the BB sleeve any advice from someone that has done it?


http://i46.tinypic.com/2eyklms.jpg

i know this is past your deadline for drilling the actual hole, but is it not possible to drill down into the bottom bracket from just below the "cutout construction" sticker?

even if this hole ends up being angled inwards i think it would still be a better option than drilling two holes all the way through both the top and bottom of your BB.

Drilled the hole and finished the Di2 build. I am still doing some tweaking. The hole drilling turned out to be pretty much a non-event. It was very easy to do. The top hole feels like there is basically zero carbon against the metal shell.

I did exchange messages with Damon Rinard from Cervelo before drilling hole and he indicated that I would not be able to go around the shell as there would not be enough room. So coming from him felt it was pretty definite.

But I did discover (too late) that you can get to the seat tube from the bottom hole for the FD. So even though there is no one that should know better than Damon I believe you can get there and pass a wire without going through the BB shell.