On Saturday, April 10, 2021 at 1:02:32 PM UTC-7, jbeattie wrote:
On Friday, April 9, 2021 at 1:54:22 PM UTC-7, wrote:
On Friday, April 9, 2021 at 12:45:48 PM UTC-7, Mark cleary wrote:
On Friday, April 9, 2021 at 12:48:15 PM UTC-5, wrote:
On Friday, April 9, 2021 at 10:10:43 AM UTC-7, Mark cleary wrote:

Mine have broken twice in the past 2 years right at about 6 months. The cable ends fray and lucky me it is flat in Illinois and I just ride home and put on a new cable. I change the last one that snapped in July 2020 so about a month ago instead of waiting for the cable to snap I just put a new one on. It is always the rear derailleur don't use the front much. Well sure enough the old cable looked fine when I pulled it out no fraying but I put a new cable one. Really a minor price to pay for not worry as much about snapping them on a ride. Actually I am pretty lucky I get 3-4000 miles before they snap or need to be change. No not going to Di2 my 6800 shifts smooth and silent.

Deacon Mark
I have no understanding of how you can do this. I did break an old steel cable that the Chinese were selling, or rather that a local was stocking and selling out of his garage. But I have never broken a single stainless cable and I have used some pretty cheap ones. I prefer the top end Campy cables and have never even come close to breaking one AFTER it was installed. As I was recovering my memories and some manual dexterity I did break some cables while installing them. But that was long ago and far away.
Well it is at the end in the shifter so it frays from the anchor point in the cable. Not like the cable just snaps into 2 separate pieces. If fact the cable really does not break it just pulls apart in the shifter and then you have to fish the parts out and make sure leave nothing behind. Shimano on the new stuff now has a part on the shifter to remove at space to get the cable head out. I have heard on earlier stuff sometimes they got stuck in and then you had to replace the shifter. There is even some place they have a way t drill through the shifter to get the cable head to spare the shifter.

But frankly if you want to know the truth on why it happens to me is because of all the power I produce in the hands on the shifter. I mean I can drop some serious power numbers up there when I take the swipe 🤣
Deacon Mark
Shimano never used this design in which both cables come out under the tape. This is a fairly new design and it is a funny design in which you poke the cable through from one side, remove a compartment cover and push the cable at a 90 degree angle up though a small passageway. I had misgivings about it when I saw it but it appeared to work fine on my 105 stuff on a cyclocross bike. I would have used what I think is called an Archimedes wheel-like mechanism.
The dual internal cable, AFAIK, started with the second generation 10sp (10 years ago) and uses a similar winding mechanism, but the cable now takes a hard turn in the lever, which is not where it breaks -- but those hard turns do put high stresses on the internal guides. The 6700 had a much more straight-forward cable path, and I don't know why they changed that up for the 6800. I think cable failure has been in basically the same place in all the STI shifters -- about a CM from the button head.

I have never seen a cable break in a 6700 series lever nor heard of it. It was a perfectly straight pull. That hard turn occurred in the 6800 and later levers and that put a large strain on the lead wire tip and the area where the turn occurred. It all seemed to work well enough but then all of the stuff I used them on had newly installed cables. How old was the cable of yours that broke?