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Slick shifting, flawless performance in all conditions and situations, lighter and improved ergonomics make Shimano's latest Ultegra Di2 6870 11-speed groupset the best yet. With all the performance of Dura-Ace at half the price and with a weight penalty that only weight weenies could worry about, Ultegra Di2 steals the show.
Ultegra Di2 6870 combines newly designed dual control levers and smaller, ligher, derailleurs and a new internal seatpost battery, and uses the same chainset and caliper brakes as the mechanical Ultegra 6800 groupset. Ultegra Di2 is also available with Shimano's latest hydraulic disc brakes, but you can read all about those in this separate review.
This review focuses primarily on the shifting performance of the new Ultegra Di2 6870 electronic groupset. The price is for the shifters, derailleurs, battery, charger and various wiring and control gubbins. You're far more likely to acquire Ultegra Di2 as part of a complete bike, though.
The new Ultegra Di2 6870 groupset gets the same updates first applied to the top-tier Dura-Ace Di2 groupset. Those changes centre around improved ergonomics in the shifter hoods, smaller and lighter derailleurs, and the E-Tube system that allows every shift button to be customised.
Using the new Di2, the first thing you notice – as they're your main point of contact with the groupset – are the much improved shifter hoods. They're noticeably slimmer and fit my hands much better than the mechanical versions (I do have small hands though). For all types of riding I found the compact shape preferable, and I really appreciate the small diameter of the main body that make it easier to wrap your fingers around when you're climbing out of the saddle.
The shift buttons have been revised; the contrast between the surface texture of the two buttons is now more pronounced. Despite these changes, which are an improvement over the previous Ultegra Di2, I would like Shimano do a lot more to improve the feel of the buttons. The two are still close together, and with thick gloves on it's sometimes difficult to locate them. Also, They're just a bit lifeless and devoid of any of the feedback that a mechanical groupset provides.
That's really my main gripe with Di2, but I know plenty of people who don't feel the same, so that's a really personal thing. Despite this, I can quite happily get on with Di2, it's not enough of a deal-breaker that I just can't put up with it. And after a while you soon adapt and just get on with riding your bike.
Ultegra Di2 uses Shimano's E-Tube (that's the wiring and communication system, based on the CAN bus protocol) which has the potential to allow the shift buttons to be fully customised. Out of the box a single press and hold of a shift button will cause the rear derailleur to move across the entire cassette. You could specify a two or three sprocket shift, you can even change the shift speed with five settings available, and many other options are available too.
The wiring is plug-and-play – so it's easy to set up – and is all controlled by a junction box that you strap to the underside of the stem. Concealed under a small flap on the side of this box is the charge port, and is also where you plug in a PC if you want to customise the shift buttons. There are optional sprint, Roubaix and aero buttons that can be plugged into the system too. The charge port is for the internal battery; if you have an external battery you need to remove it to charge the system.
The updated derailleurs have been given the same smaller dimensions as the latest Dura-Ace Di2 versions, and are now significantly less bulky in appearance. Visually they look a lot better on any bike, still chunkier than mechanical but much less so than previously.
The rear derailleur is much slimmer and a better looking unit, with neater wiring. It of course goes up to 11 now, a change first introduced on Dura-Ace and now available at half the price. There are two versions of rear derailleur available, the long cage option accommodating a 32t cassette and the standard short cage going up to 28t. The long cage will make an ideal climbing or cyclocross option, the latter paired with the Ultegra 46-36t chainset.
A neat feature of the rear derailleur is the a crash protection facility that automatically disengages the motor so the mech can move out of the way to avoid an expensive replacement bill. With a rear derailleur costing £175, that's a good thing.
Provided you've found the right button, a light press results in an immediate and very slick gear shift. It doesn't take much effort to change gear, and while in perfectly dry riding conditions a good mechanical groupset is very similar in performance, it's when the weather turns bad that Di2 runs away with a clear performance advantage.
A couple of rides and races run in heavy rain and cold temperatures proved that Di2 is simply better when you have very little feeling left in your fingers. I've done rides so wet that I've had inadequate feeling in my fingers and hands to change gear on a mechanical groupset (a particularly wet 200km Audax) but Di2 in the same conditions allows you to still change just fine.
Don't get me wrong, it's not just in foul conditions that Di2 impresses. Even in the most perfectly glorious cycling conditions, Di2 is - once you've got used to the shift buttons - a joy to use. Every gear change is perfect, there's never a missed gear, which is useful when you're climbing and reaching desperately for an easier gear. The buttons are reached easily from the hoods, thanks to the more compact form factor, and equally from the drops as well.
The auto-trim feature on the front derailleur is one of the best features of the entire groupset, and avoids chain rub that can't always be eliminated on a mechanical groupset. The brain of the Di2 groupset knows what gear the bike is in and so it can centre the derailleur precisely around the chain. You can customise the trimming function but it works so well out of the box that we felt no need to.
You might be forgiven for not even noticing the addition of an extra sprocket when you're using the 11-speed groupset, but there are times when the smaller jumps between certain gear ratios just helps you find the perfect ratio so you can maintain the right pedalling cadence to match your current speed and power.
That flawless performance and complete lack of degradation, of the sort you can't expect with a mechanical groupset for every ride – unless you're fastidious in maintaining and servicing the cables – is really Di2's trump card. It always works brilliantly every time you hit the road, whatever the weather or conditions. That makes it an appealing choice of a bike you want to ride year-round, through the full gamut of British weather. There's no cables to degrade or cable outers to shift in their housings. Once it's set up to shift perfectly, that's what it continues to do for mile after mile.
In my opinion this is the best electronic groupset on the market. It's all of performance of Dura-Ace but at a much reduced cost and with only a weight penalty that the seriously weight conscious need worry about. Really, unless you're building a superlight superbike, you'd be daft to buy Dura-Ace over Ultegra.
Switching from mechanical to electronic does take a little getting used to, but a few hours in the saddle and you'll be just fine. While I'm not the biggest fan of the way the shift buttons 'feel' when you operate them, there is no denying they work brilliantly when pressed, delivering rapid and precise gear changes each and every single time. No matter the weather, rain or whether coated in mud.
The battery life is excellent, long enough that you only need charge it occasionally. The internal seatpost battery does make charging a little less practical for some - you can't easily remove the battery and have to keep the bike near a power source so you can plug the USB lead into the control box under the stem, but that's a minor impractically. You can still buy bikes with external batteries, but they're becoming markedly less common.
Personally I prefer the feel of a well maintained mechanical groupset, but there's the crux of the matter; Di2 is virtually maintenance free and will work the exactly the same in six months time, with no adjustment or servicing required at all. For British cyclists, that's a very appealing proposition.
Excellent shifting performance
Programmable shifting action
Long battery life
Lighter than previous version
Half the price of Dura-Ace
Gear shift buttons could have a more distinct feel
Stunning, flawless performance in a lighter and sleeker package
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Make and model: Shimano Ultegra Di2 6870 11spd groupset
Size tested: grey
Tell us what the product is for, and who it's aimed at. What do the manufacturers say about it? How does that compare to your own feelings about it?
Our Ultegra Di2 series with electronic shifting is "pro-proven" as it is a direct trickle down from our Dura Ace group. It stands for state-of-the-art technology, proven in pro races, the technologies used in the new Ultegra 6870 series 11 speed, newly designed brakes, new chain treatment etc. The electronic shifting lets you concentrate on your performance.
Tell us some more about the technical aspects of the product?
Ultegra Di2 11-speed front dérailleur
The Di2 front dérailleur's operation is pioneering, smooth shifting is guaranteed thanks to a microchip communication link with the gear levers.
What's more, shifting the rear derailleur automatically trims the front derailleur
The biggest difference you will notice is just how much quicker and effortlessly smoother shifting on the front chainrings is, even under load
The difference in the effort and time to actuate the shift between mechanical and Di2 is truly staggering
Ultegra 11-speed rear dérailleur
With Di2 technology shifting is easy and precise - just a light touch, as soft as a mouse click, is sufficient for the front or rear derailleur to instantaneously select the correct gear
Programmed automatic motion at the touch of a switch makes this derailleur quick, smooth and effortless to shift
The removal of traditional mechanical cables in favour of electrical wires not only eliminates poor shifting caused by contaminates, corrosion and stretching, but provides effortless gear shifts
Derailleur contains a saver (fuse) function, where the inner structure is protected from strong impacts
11-32T wide gear ratio capacity will cater for compact setups as well as the traditional road double
High tolerance cold forged aluminium link plates and body construction is extremely light and durable
Four self-lubricating micro-machined fluorine-coated link pivot bushings provide low-friction shifting
11-speed E-tube Di2 compatible
SM-BTR2 Di2 internal mount battery
The power house of Shimano Di2 is a long-life 7.4V Li-Ion battery that is both compact and reliable, taking shifting effort away from you
Excellent sealing and reliability have been proven through repeated field tests in various riding conditions, including extreme temperatures, rain, mud, and cobble stone roads
Using a hard wired battery system which is both light weight and accurate compared to current wireless technology (as a wireless system would require 4 batteries: one for the RD, one for the FD, and one for each shift lever)
The use of a single small and discreet internal battery is light weight, efficient and creates a robust and reliable system
One charge can give between 1000 and 2000 kilometre range depending on conditions and front mech operation (as this is the main power drain)
500 times rechargeable life
Battery is to be mounted with seatpost or frame manufactures hardware normally inside the seatpost or seat tube
Performance is excellent, some might find the lack of tactile feel with the shift buttons an initial concern.
No concerns with durability or its ability to stand up to all weathers at all.
There is a weight penalty over Dura-Ace Di2 and the mechanical Ultegra 6800 groupset is still a lighter (and cheaper) option.
Tricky one this. If you shop around, Ultegra Di2 is half the price of Dura-Ace Di2, which makes its bargain. However, Ultegra mechanical is half the price of Ultegra Di2, so that's a serious leap in price for a marginal increase in performance.
Tell us how the product performed overall when used for its designed purpose
Delivers impressive performance.
Tell us what you particularly liked about the product
Zero maintenance, long battery life, good performance in all weathers and situations.
Tell us what you particularly disliked about the product
Lack of 'feel' in the shift buttons.
Did you enjoy using the product? Yes.
Would you consider buying the product? Maybe, but I'd have a long think about Ultegra 6800 mechanical first.
Would you recommend the product to a friend? Yes.
Anything further to say about the product in conclusion?
If you really want an electronic groupset, this is the best you can get right now, but it faces stiff competition from its own mechanical groupset which is very nearly as good, but a lot less money.
Age: 31 Height: 180 Weight: 67
I usually ride: My best bike is:
I've been riding for: 10-20 years I ride: Every day I would class myself as: Expert
I regularly do the following types of riding: road racing, time trialling, cyclo cross, commuting, touring, mtb,
David worked on the road.cc tech team from 2012-2020. Previously he was editor of Bikemagic.com and before that staff writer at RCUK. He's a seasoned cyclist of all disciplines, from road to mountain biking, touring to cyclo-cross, he only wishes he had time to ride them all. He's mildly competitive, though he'll never admit it, and is a frequent road racer but is too lazy to do really well. He currently resides in the Cotswolds, and you can now find him over on his own YouTube channel David Arthur - Just Ride Bikes.