Groupsets

The main groupsets are Campagnolo, Shimano and SRAM.

They all now have electronic groupsets.

Shimano, the originator of the Di2 which forced the others into the business uses a wired system like the Campagnolo EPS.

Shimano is a highly technical design that settled upon a method of powering and communicating with each component over the same two-conductor wire. Originally it used multiple wires and I can just picture an electronics engineer looking at that and asking Shimano management, "Why?" In any case since each part communicates with the others, you absolutely must have interchangeable components. These can be anything from 105 to Dura Ace but everything down to the battery itself much be a component interchangeable with the particular group. Why they would have different groups that are not interchangeable I couldn't say. You can get the 9000 series Di2 or the 9780 (which I have). Of course this might be nothing more than mistaken documentation on the Internet which is famous for that.

Campagnolo EPS is also a wired group and I know very little about it except that it is a 12 speed group and cost slightly less than a Tesla S model with full extras. As I've said before, my opinion of Italian engineering is that they are more artists than engineers and I wouldn't be surprised to discover that they need to go through many iterations to get it to work reliably. Though it would look pretty.

SRAM groupsets are real trash from my point of view. Their cranks for instance, have different size bearings on each side of the bike and the steel of the cranks is relatively soft so that they wear away rapidly leaving the cranks to rattle loosely in the bearings. Their electronic shifting idea became rather strange as well. Whereas Shimano has a single battery that lasts probably too long leaving you to eventually run out of juice a month after the last recharge after you've forgotten you even need to recharge, the SRAM is wireless and everything has its own battery to die on its own. They also have the odd idea that the right level shifts to a lower gear and the left to a larger gear. This means that there must be extra intelligence somewhere in this rig to calculate which is a larger gear - the upper chainring and the larger cog or the smaller ring and the smaller cog. Good luck if the battery for that component gives up the ghost. And some of these components uses a coin cell. Hope you're battery rich. Judging from my TV remote which has a three AAA cells and only lasts a month or six weeks, coin cells that go flat shifting you into a granny gear to limp 20 miles home doesn't seem all that brilliant to me.

The Chinese presently have a manual high end groupset from a couple of companies but the tests on them aren't very pleasant and it is likely that the means they are using to get around SRAM and Shimano patents in the USA make for not very well working setups.

Sooner of later I suspect that Shimano will replace the Di2 and Manual groups with hydraulic which will solve most of their problems since people are now seeing just how simple it is to bleed hydraulic systems. Changing the derailleurs to hydraulic would make the changes so soft that it would make Di2 seem like a real effort. Also you could build in chain rub compensation so that it relieves a little pressure if it detects the chain rubbing. Of course this implies that it always has to be setup so that rub is from the high pressure side.

The end result would be a shifting/braking system that has extremely light touch without ever having to recharge a battery. What do you gain by electronic shifting other than automatic compensation for front chain-line?

It would also allow a piston design for the derailleurs that was made out of plastic so it would be lighter and last forever. Maybe that is why they are holding back.