If this is succinctly covered somewhere else please forgive and direct me. I have a specific question regarding Ultegra. Di2 6870 compared to 6800....is the difference in going to electric/electronic really significant and what would be any practical drawbacks? Other than cost. I'm a dedicated(?) rec and fitness rider these days kinda planning to get a new endurance bike, prolly a BMC GF02 this coming season. Any comparative insights would be most appreciated.

I think it's really about what you prefer. The new 6800 mechanical system is really smooth and low effort. The electronics, of course, give perfect shifts every time. Personally, after putting decent miles on both, I settled on the mechanical system because of cost, but also because I actually like the more direct feel of a mechanical system. Of course, I drive a stick shift car daily as well. Others love the electronic setup for the tech or the lack of adjustment and cable maintenance, etc. I have heard that replacement parts for the electronic system are expensive and sometimes hard to get, but that could be wrong, so don't take it to the bank unless someone else can confirm. Bottom line, it's up to what you personally like. No bad choices here.

Downsides to electronic shifting: weight, price, reliance on a battery. From what I hear they're pretty well thought out in that if the battery dies while you're riding, it will shift to a middle gear so you can limp home. Most people who go with electronic shifting don't go back. I've heard the latest Ultegra and DA are so good that the Di2 stuff isn't a slam dunk anymore.

Anyway, mechanical Ultegra is really really good. If you haven't used the electronic group yet, and have nothing to compare against, you'll almost certainly be happy.

I recommend you test ride both, and choose which you like better. You may find the electronic shifting to be awesome in operation, so you spend the extra money and deal with the associated complexities (weight, battery life, obsolesence). Or, you may find that they operate about the same, and you'd be happy with the mechanical group and more money in your pocket for other upgrades.

I mentioned obsolescence because a mechanical group can always be supported and repaired, so long as you have the correct (or equivalent) parts. An electronic system will eventually be non-supported by the manufacturer, so you won't be able to get new firmware support. Compatible parts are much more specific for electronic groups, and you may not find compatible parts in the future because there won't be third-party offerings.

A new bike with either group is a serious investment.

Personally, i'm not much of a roadie (I prefer gravel and dirt), so my new component purchase would be the RS-685 hydraulic disc brake/mechanical shifting controls. Shimano makes a Di2/hydraulic version (RS-785), FYI. I just don't think that Di2 offers much value for the added cost/complexity (in my opinion, according to my riding style and self-maintenance)

There are many other Di2 threads. It's rare to find anyone that switched back to mechanical. For other riders, Di2 isn't worth the extra expense.

Very few riders have posted having trouble with their Di2. It seems to be very reliable. (Just keep the battery charged -- there's a green/red status light on the junction box for the battery charge level.)


I have Di2 on my road bike, and mechanical shifters on my "touring & gravel road" bike.

Di2
I've always shifted a lot, trying to always stay at my preferred cadence. Now, with Di2, I shift even more often. I'll shift the back for just a couple of pedal strokes, then shift again. And I often shift the front chainring for very small roller climbs, even 40 or 50 feet high, and stay seated. I have the Di2 set to "shift 3 with a long press", so pressing the bottom button on both the front and back for 1/2 second (a "long press") moves the front from 50 to 34, and the back to 3 cogs smaller, just right for the base of a hill. Pressing the two top buttons does the opposite when I hit the downhill.

I did a 100 mile ride this summer that was 7500 feet of rolling hills. Very little flat ground. I was shifting the front a lot all day, it was great.

On fast (for me)group rides, the instant shifting helps me to hang on.

The shifting is like clicking a mouse. The rear shift is instant, and the front is quite fast and certain, and works under load too. And it auto trims as I shift the back, so there's no chain rub.

Mechanical
On my other bike, for gravel roads or for touring / all day rides, I've slowed down and don't need to shift quite as much. I tend not to be riding at a full effort on this bike, so I can use a wider range of cadences. I don't really miss the electronic shifts. Front shifts are a lot more effort, so I don't do them nearly as much.

Thanks for the thoughtful responses so far folks. Within some bit of reason, cost isn't that big of an issue. Also within reason, neither is an added bit of weight. As noted, I'm a rec/fitness rider these days and really just into enjoying the daily ride. Current road bike is a three year old Tiagra equipped Cannondale Synapse and I find the shifting "adequate". Looking to move that to backup status for something better and contemplating going with an "in for a penny, in for a pound" philosophy.

What constitutes "really significant" is subjective. I can't imagine improving on the current DA mech group, but it is mechanical, which means you're moving the derailleurs and derailleur adjustment and cables will need periodic attention. I like the DIY shifting and don't mind the DIY maintenance. With electronic, after installation there's really no DIY except for charging the battery.

One point that has not been brought up, while you'll pay more for the electronic, you won't need to replace shift cables on a regular schedule with Di2. The most sad thing about the new 9000/6800/5800 mechanical is how the cable will get chewed up in the shifter becoming a SOB to extract. There have been several threads on here about that.

I've run mech 6800 and now have mech 9000 and both are super precise and very fast shifting when set up correctly.

I ride with people that do Di2 and a few times somebody has showed up at a ride with a dead battery.
The typical solution is to borrow a battery, put the bike into a middle of the range gear, and then give the battery back. OK on flat rides in Hutto, doesn't work so well in Dripping Springs.

If you are the type of person that forgets to charge your cell phone, it could be an issue.

That's a significant factor to consider.

Consider with mechanical shifting or braking, you'll be tuning and/or replacing the cables more often (esp with new Shimano), but it's something that you can easily do at home.
With electronic shifting or hydraulic braking, you'll be doing less maintenance but it may require you to take it to the shop instead of doing it yourself.