Jim’s Tech Talk
By Jim Langley
Way back in 2009 Shimano introduced their first electric-shifting Dura-Ace 7970 Di2 groupset. Di2 is short for Digital Integrated Intelligence (Di2 = DII, get it?).
In case you haven’t tried or followed the electric shifting trend, I’ll explain what DII means in terms of advantages (feel free to scroll ahead if you’re already electrified).
I’ll try to explain based on today’s Shimano e-shifters since things have changed a lot in the years since Di2 debuted. We now also have SRAM’s amazing eTap shifting, which is wireless, but I’m mainly talking about Shimano today. Late breaking news: Shimano just announced their Dura-Ace 9200 and Ultegra 8100 groups that are semi-wireless. AND, maybe even more shocking, that they will no longer be making mechanical Dura-Ace and Ultegra parts!
Derailleurs with Brains
DII is what makes electric shifting worth considering for anyone interested in easier, more precise and quicker shifting. Integrated Intelligence basically means that electronic brains inside the derailleur(s) “read” what chainring and cassette cog combinations the chain is on as you shift and they automatically adjust the derailleurs’ positions accordingly. You can also choose built-in shifting modes.
Advantage: Never Trim the Front Derailleur
In case it’s Greek to you, “trimming a front derailleur” means to move its lever just a little (not enough to shift) in order to nudge the derailleur cage away from the chain and stop the chain from rubbing, a common annoying noise when the chain’s on the smallest/smallest and biggest/biggest chainring/cog combinations (sometimes called “cross chaining”).
With electric shifting, you never have to worry about trimming to stop rubbing noises because the front derailleur is smart enough to move away from the chain on its own as you shift into a gear that would rub otherwise. Once you have it you wonder how you lived without it. (It’s only fair to point out that mechanical auto-trim shifting exists, too – and goes back decades; but it’s not on every system and not as foolproof.)
Advantage: Never Miss an Important Shift
Have you ever had a cable derailleur hesitate and refuse to shift just as you tried to hit your smallest cog to go for a town line sprint? I sure have and it’s frustrating to say the least.
Well, Shimano’s electric rear derailleur will hit that 11-tooth hyperdrive letting you go for glory every time because it overshifts! How can it overshift without throwing the chain, you ask? It’s the magic of Di2.
The brain recognizes that it’s about to throw the chain and it instantly corrects itself, backing up to where it belongs, directly under the 11 tooth cog.
Advantage: Never Miss a Gear
An example of even more-advanced Shimano electric gear changing is their Synchro Shift mode. This actually allows sequentially hitting every gear on your bike (such as 1st, 2nd, 3rd and so on) – and doing so while operating only one shift lever.
In this mode, the front and rear derailleurs can even shift simultaneously, which is pretty amazing – and fun. It also means a double-chainring bike will shift essentially the same way 1X drivetrains shift.
That’s not a complete list of advantages but should give you an idea why e-shifting has made its way onto lots of bicycles. I was eager to try it when it first appeared and bought a groupset for my time trial bike. I believe it made me faster (my race results showed it) by allowing shifting without changing my hand positions (which creates air drag and slows you down).
Since it worked for me on the TT rig, I now have Di2 on a road bike, too. That bike was purchased used so it turns out that I’m running the original Dura-Ace Di2 from 2009, not the latest version (but I have ridden the latest Di2 with Synchro Shift a lot).
Short on longevity (pun intended)?
Up until a couple of weeks ago, my at-least 7 year-old Di2 (about how old the bike is) was shifting flawlessly. Then the front derailleur started making an awful creaking sound when I shifted, like an old rusty door hinge. Since I had been riding on dirt roads, I thought grit had contaminated the derailleur pivots.
I cleaned the pivots and lubed them but the noise persisted. Then the derailleur balked when I tried to shift from my small to large chainring. Looking down, I could see it trying to push the chain so I reached down and gave it an assist with my finger. That did the trick. It’s a risky move but I carefully shifted like that for a while.
In the meantime I reached out to Shimano and learned that my front derailleur’s symptoms meant that it was worn out and needed replacing.
The whole story of my worn-out derailleur and replacing and adjusting it is in the video here. It was a fun project and I hope you enjoy it.
I’m not writing about and didn’t make a video about this project to complain or to run down Shimano or e-shifting. Rather I’m hoping to help anyone else who might have a Di2 front derailleur that starts acting up like mine.
Plus, I think it raises some interesting questions. I have my opinions. But I would be interested in what other riders think – and both those of you with electric shifting and those without.
Please read the questions that follow and then comment to share with the rest of us. Feel free to raise other issues you believe add value. Already on my video there’s been some interesting feedback. I think the conversation will be helpful for anyone who’s thinking of trying e-shifting. Thanks!
Electric Shifting Questions
• Have you had an electric derailleur fail and if so, how did it fail? Which brand and model?
• How long should electric shifters last (keeping in mind the long lifespan and low cost of mechanical derailleurs)?
• Do you think electric shifting is overpriced, or maybe a better question, is it ever coming down to affordable prices the way costs rapidly drop on most electronics?
• How long should electric derailleurs be warrantied?
• Should electric derailleurs be repairable/rebuildable (new motors, electronics, etc.)?
10,109 Daily Rides in a Row
Jim Langley is RBR’s Technical Editor. He has been a pro mechanic and cycling writer for more than 40 years. He’s the author of Your Home Bicycle Workshop in the RBR eBookstore. Check out his “cycling aficionado” website at http://www.jimlangley.net, his Q&A blog and updates at Twitter. Jim’s cycling streak ended in February 2022 with a total of 10,269 consecutive daily rides (28 years, 1 month and 11 days of never missing a ride). Click to read Jim’s full bio.