Cycling Tech – di2 shifting


After some years of scepticism I am a recent convert to electronic shifting.  My new bike came with the Ultegra 6870 Di2 group set

The best part about Di2 is that the gear changes are made electronically rather than manually.  Electric motors in the front and rear derailleurs do the shifting for you rather than shifting by manually pulling cables.  The cabling connection from the shifters to the derailleurs is purely to pass on power and the electric signals.

This means that each shift occurs with absolute precision and the gears require much less adjustment than manual gears do.  The system is powered by a battery and computer  that sits inside a junction box.  Connecting cables plug into that box and go into the front left and right shifters and also into the derailleurs at the front and rear of the system.  The whole thing is designed to be “plug and play” so all you have to do is connect the various parts to the junction box with Di2 cabling and the whole thing works.  No need for the hassle of adjusting cable tension etc.

The junction box is small enough to sit inside a seat post or a down tube so that it doesn’t have to sit mounted on the outside of the frame as earlier Di2 systems did.  It is still possible to fit the junction box to the outside of the frame as it is waterproof but it is much more aero if it can be shoved inside a seat post or a down tube.  Most bikes nowadays are designed to work with Di2 and even older bikes can be set up with a Di2 system by your local bike shop.

The cost of the system when buying a new bike is not that much greater than a mechanical group set.  It costs roughly an extra $500. The retail price of an Ultegra Di2 system is about AUD$2,000 but in reality you can buy them on-line for half that.  When looking around for a Di2 system when I bought my last bike six months ago you could buy a Di2 complete Ultegra system for about $900.  That is about the same price as a complete Durace mechanical system (not the new 9100).

So what’s it like to ride?  Well it’s fantastic.  The gear shifting is absolutely precise.  It’s quicker than a manual shift, the shift is instant. Unlike a manual system where you’ve got to throw the shifter lever a fair distance to make a shift and quite often the gears quickly get out of adjustment and the amount of pressure you have to apply changes, a Di2 system is always the same.  You just press the shifter, you click a button where the lever used to be and the shift occurs.

The battery life is really good.  In practice I found that I have never got close to having the battery running out of power.  I usually charge the battery once a week but if you read the literature Shimano claim the battery will last about 1800km on a single charge.  The exact battery life depends on how often you shift gears but I did read recently that a Shimano Di2 equipped bike in the Tour de France did the entire tour without a recharge of the battery without any problems.

The junction box has a light indicator on it to tell you how much charge is remaining.  It has a solid green light if the battery is 100-50% charged, a blinking green light if it is around 50%, a solid red light if it is around 25% and a blinking red light to indicate that it needs charging ASAP.  There are still 200 shifts available on the blinking red light and when the battery gets really low the front derailleur is disabled first so that there are still a couple of hundred shifts available on the rear cogs before the battery fails.

The only reason you should ever run out of battery on Di2 systems is if you neglect to charge it at all for months and you ignore the warning lights.

You can get an adaptor that allows the Di2 junction box to connect wirelessly with other devices via ANT+.  I have installed this.  It costs about $50 and it will talk to my Garmin bike computer and also my Garmin watch.  That allows the Garmin bike computer to give you a heap of data on the go.  This includes what gear you are in, your gear ratio (that is the mechanical advantage from front gear to the rear gear), the battery charge percentage, the number if shifts you have made on the front derailleur and the rear derailleur during the ride and a few other sort of useless bits of data that are entertaining to data nerds like me.

For example on a bunch ride to Mornington and back of ab

out 84km, I made eight shifts on the front derailleur for the whole ride and 844 shifts on the rear derailleur for the whole ride.  So that is 852 shifts over a three hour ride.  I’m not sure exactly what that means but that to me is pretty interesting that I would change gears 844 times in 180 minutes.

The newer Di2 systems in future will allow for more advanced gear shifting systems.  You can already program a Durace Di2 system to make combination gear shifts.  The same is available in the r8070 Ultegra system.  For example, press a function key and have the front derailleur change down and have the rear derailleur change three cogs up at the same time.  The technology allows for a semi-automatic or fully-automatic gear changing system that responds to the load that you put through the chain and select the appropriate gear.  You might imagine a system that automatically changes you down to the small ring on the front and drops you down a couple of gears on the back when you start climbing.  The current Di2 technology would work with that with some software adaption but future systems will do that straight out of the box.

A link to an automatic shifting system reviewed –



5 thoughts on “Cycling Tech – di2 shifting

  1. Pingback: Cycling Tech – di2 shifting | Australian Law Blogs


    I’m a huge Di2 fan, I’ve got the older-gen 10 speed Ultegra Di2 on one of my bikes and it’s covered 1000’s of miles in all sorts of weather without missing a single beat. If my best bike wasn’t externally cabled I’d have it on that too (SRAM eTap, while even more awesome, is a little too $$ for me).


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