I have Shimano Ultegra Di2 on one of my bikes. It’s an older fully wired version.
It’s wonderful.
Once set up it works faultlessly and doesn’t require the readjustment or cable servicing that’s required with a cable operated drivetrain[1].
On top of that the front derailleur constantly trims itself to never chain rub and semi-automatic[2] shifting is surprisingly useful.
Also Di2 let’s you add multiple shift buttons. So you could have shifting at every hand position if you wanted.
Finally the thing that sold it to me. I did a multi-day ride on my old bike. After the first 4 days I got cramp in my hand everytime I shifted. Told myself I’d try di2. Every gear change is now as soft as a mouse click.
All that and the only real downside side is you have to change it every 6 months.
It’s a very well thought through system. I know lots of people with Di2 in my bike club. I don’t think anyone dislikes it.
1. Bowden cables don’t “stretch” as such, what actually happens in mechanical systems is that the ferrel ends settle over time or the linings of the cable outers wear and flake causing friction.
2. The semi-automatic mode means single buttons for higher or lower shifts. The front derailleur shifts as appropriate to give you the next ratio.
You can repeat that on each hand or on the top hood position. So for example, if you want to change gears as you indicate left or right, now you can.
I just installed the same version on my bike six weeks ago. For me the best thing is 100% reliable and fast front derailleur shifts. I’m pretty good at setting up a rear derailleur, but no matter how much I fiddled I could never get a cable-actuated front mech to shift into the big ring nicely. I would always get that annoying thing where it takes a second extra for the chain to catch on the big ring, or if I had it shifting nicely it would rub. Plus, since it’s just pressing a button with Di2, I can easily change into the big ring from the drops since I don’t need to push the whole lever sideways.
With Di2 I haven’t dropped a chain and it shifts instantly, just whzz and it’s ready, with the automatic down shift at the back too. The auto-trim feature is great too, no rubbing at all.
Honestly I don’t have a bad thing to say about Di2 at all, I’m far from a competent mechanic and between my group set arriving through the door and taking it for a first ride it took me about two hours to install everything. Just to change the cables previously would take me an hour of fiddling around with magnets to try and get them routed through the frame.
Mine came with the RX derailleur which includes a clutch mechanism.
That really helps with both dropped chains and chain slap. Neither really happens any more not matter what surface I ride on (road, gravel, cobbles or light single track).
Yeah, I was too till I tried it. Thousands of miles of instant, perfect shifts at the light touch of a button with no adjusting, no cable clutter, no cleaning, etc. is very nice. It would all be worthless if the electronic shifters were in the least bit unreliable but the two systems I’ve used have both been rock solid.
Electronic shifting systems even add reliability vs. mechanical ones by allowing a knock to temporarily displace the derailleur, which the motor will then fix nearly instantly, rather than breaking/bending while futility trying to resist a high force.
Right. A guy I know had this fail while riding up a mountain (I believe he said the battery died) and he could not change gears at all even though he tried.
He effectively had to limp his bike home because he was stuck in the gear he had riding uphill. Took him half a day or so rather than an hour.
I’m certainly not a Luddite but this doesn’t seem to be a worthwhile trade off for me.
The good thing with my current bike is that it never runs out of fuel, by design. I can pick it up anytime and it just works, it was so 10 years ago when I acquired it, and it'll be so 10 years down the road.
I have a Garmin Forerunner 735XT watch and it needs charging every 15 days, which is better than any "true" smartwatch out there. At some point in the distant-but-not-so-much future the battery will flat out die and there will be no replacement part. The experience from my mechanical watch is entirely different: it keeps on ticking as I move around, and the thing will probably end up surviving me.
Going from zero to non-zero - whatever the value of non-zero is - is non-negligible mental weight. Zero is a freeing experience.
Although with 20 years of use, those gear cables are likely to fail. Presumably you do things like lube the chain, inspect your tyres, keep them inflated to the correct level?
I've had a couple of Di2 batteries fail. One of them went suddenly and I had to grab a train to get home. The other one lost capacity quite quickly, so I'd have to charge it once a week until it got so bad I needed to charge it fully each day until I swapped in a new one.
So when that happens only the back or front runs out of battery. Usually it will be the back and you just swap them and ride home without being able the shift on the front.
Back and front are powered by the same battery which typically lives in the seat post. When the battery gets too low, the front shifts are disabled first as they take more juice.
Not on mine, SRAM etap, there is a small rechargeable battery in the front and back. They are the same so can be swapped.
I really, really like it. I know I paid way too much for that bike but it is amazing and I can really feel the difference in a way I never could before.
Why aren’t these bikes using a hub generator to produce the necessary energy to automatically recharge the batteries for the bike computer and shifting motors? Or am I missing something?
Di2 is mostly popular among the performance cycling set who likes to go fast. The ~5% drivetrain power loss you'd get from a dynamo isn't attractive in that market. Also, Di2 requires charging every couple of months. It just isn't worth it.
I have seen some randonneuring bikes with a dynamo with USB charging for topping up the bike computer and the like. Commuting and utility bikes tend to just use the dynamo for lights.
That’s a market that’s entirely foreign to me, I use my bicycle entirely for commuting, buying groceries, etc so I’ve got a hub dynamo powering the lights.
I’m honestly surprised that there’s no super-low-power hub dynamo for this segment, but if it’s all people using bicycles for planned trips, they can take charging into account when planning trips.
That’s pretty close to the shimano system. Most components are connected via a power cables to a central battery. The only full wireless component are the shifters on handlebars.
Sram is fully wireless, and has batteries on each component.
Both systems have their set of pros: less batteries and central charging vs less installation effort due to no cables.
Although I don't have a wireless groupset on my bicycle, I'm attracted to the idea of dual batteries (like in the SRAM system) - at least that way if you forget to charge a battery - you can swap them between front and rear so you have a slightly better ability to limp home.
With Di2 it kind of does the same thing, when your battery is getting low the front derailleur will stop working. Not sure how many shifts that leaves you at the back though so you might still be in trouble if you’re far from home.
The front derailleur stops working at a nominal 10% charge. You'll have plenty of rear shifting left on all but the longest rides.
That being said, it's really easy to avoid the battery getting that low. It lasts months under normal conditions. And your head unit will tell you when the battery gets low. Except Hammerhead units won't get that warning anymore? #thanksshimano.
Haha, myself as well. There are some advantages for racers especially as you can essentially program gear shift triggers as you move up the cassette in your small ring and eliminate the need to trim when the chain line gets funky. But these are really small advantages with a lot of tradeoffs to make.. unfortunately the mechanical group set is actually being eliminated from new product offerings especially at the higher end. Thankfully there is always the second hand market.
Yep and you can also set it to just use one shift lever for up and down shifting. It will shift front and rear as appropriate to get you a higher or lower gear. In practice this means sometimes it shifts the front and then moves the back up or down 2 or so gears.
Well there's not many more advances to be made "at the higher end". You'll see trickle down and the equivalent of current Dura-ace level in the 105s inside of a decade.
...ok, now I'm officially a curmudgeon.