Originally Posted by
mstateglfr
A mountain bike front derailleur may not work well with a road crank due to the curves of each. an MTB triple FD is typically going to be a tighter curve than the large ring of a road crank's chainring since a road crank's large ring is typically 50 or 52 teeth and an MTB triple often has a 42 tooth large ring.
Then there is the issue of how many 'clicks' Ultegra Di2 shifters have. Di2 is all computer based and limited to only what the system can handle, so if Ultegra Di2 shifters are like regular Ultegra 6800 shifters and only made for 2 chainrings, then you are SOL on using a triple up front.
I admittedly know little on the complexity of Di2. It isnt anything I am interested in using and my interest is limited to just understanding how it works rather than wanting to own it. I am a tinkerer at heart and from what i do for sure know, that is the antithesis of tinkerability.
I was envisioning a mountain crank, just not sure which, and haven't researched the details of each or of bb compatibility, etc.
I'm not sure I agree about tinkerability, although I also clearly need to learn more. It's not as though cross-compatibility is a strength of modern index shifting systems, either, and if the electronic systems allow you to mix and match shifters and derailleurs more easily, that's a strength. My understanding is that the guts of the Di2 system are in the derailleurs, and they would tell the computer how many clicks they have, so the shifter doesn't need to know anything about that.
The xshifter system is interesting, if I could use it with brifters. Pushing a rinky-dink button doesn't sound much better than bar end shifters to me. I wonder why they don't include a wired option. I bet that the Shimano Di2 shifters are just using TTL logic or something that could be easily used by any other controller.