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Shimano's Dura-Ace R9150 Di2 groupset is lightweight, performs superbly across the board, and its operation is easy to customise.
The latest iteration of Shimano's flagship road groupset, still 11-speed, is called Dura-Ace R9100 while R9150 refers to the components within the group that are specifically for Di2 electronic shifting (naturally, mechanical shifting is still available).
I'll set out my stall straightaway: I think this is the best groupset out there. The shifting is smooth and reliable, the braking is powerful and easy to modulate. It's not cheap, of course, but for a no-compromise, top-level groupset, it's not ridiculously expensive either.
Weight 230g (pair)
The shift levers have been extended a little over those of previous generation Dura-Ace and there's a more definite click than before when you shift gear. It's still not as clicky as you get with Campagnolo EPS, for example, but you're not left in any doubt as to whether you've pressed it or not.
The only trouble I've ever had is when using the system while wearing massive winter gloves. The upshift and downshift levers are right next to one another – as they always have been – and I've occasionally found it hard to make sure I hit the right one. In thinner gloves and bare fingers this is never a problem.
You can adjust the behaviour of the multi-shift function – where you keep the lever pushed in to perform shifts across more than one sprocket – via Shimano's E-Tube Project app.
I'd better say a little more about connectivity for this to make sense. The front and rear Di2 derailleurs (see below) are connected via Shimano's EW-WU111 wireless unit, which allows for a wireless ANT private connection with third party devices.
These Di2 components can be connected to Shimano's E-Tube software which looks after the programmable aspects of the Di2 electronic gear shifting system. You can run the user-friendly E-Tube app on a PC (Windows), tablet or phone (iOS and Android versions are available). This makes customising the way Di2 performs much, much easier than before. You can do it yourself rather than heading along to see a local Shimano dealer with the relevant software.
You now have the option of three different shift modes, a feature that has come over from mountain biking.
Manual is yer old skool setup: one lever moves the rear derailleur one way, another lever moves it the other way, and it's a similar setup for the front derailleur. As previously, you can tinker with the system and have your left-hand lever control the rear derailleur if you like. In fact, either of the two levers or the now more prominent button positioned under the cover at the front of the hood can move either derailleur in either direction. You can adjust all this in the app.
If you go to full Synchro Shift, you simply press a button for a lower gear and the Di2 system will move you to the next lowest gear available, even if that means shifting chainrings (and avoid cross chaining, if you set it up that way). So one push of a button and the system could move you from the large chainring to the small chainring, and from a large sprocket to a smaller sprocket. Geddit?
The semi-Synchro Shift option might be of more interest to road bike users. With semi-Synchro Shift, when you move the front derailleur the rear derailleur will automatically move the chain a certain number of sprockets at the same time.
So, say you're moving from the small chainring to the large chainring. If you do nothing else, this will increase the size of the gear by a considerable margin, right? With semi-Synchro Shift enabled, the system will move the chain up the cassette to reduce that margin and keep your cadence more consistent.
Moving from the large chainring to the small chainring would usually reduce the size of the gear by a large chunk so Di2 will automatically move the chain down the cassette to reduce the jump. If you're an experienced bike rider you probably do this yourself without even thinking about it.
Switching between manual, semi-Synchro Shift and Synchro Shift is easy, you just double-click a button on the Junction A unit. You could just about do it while riding although the idea is that you do it while stationary. Chances are that you'll stick with one mode for ever.
I've tried semi-Synchro Shift but my gear shift techniques are so ingrained that I still find myself moving the front derailleur and then immediately shifting at the rear manually when the system would automatically take care of that. It's not a problem – you can override the system – but it defeats the object. A certain amount of re-education would be needed to establish new habits. I see it as being more useful to someone coming into the use of dual derailleurs for the first time.
Although Synchro Shift doesn't do it for me personally, kudos to Shimano for bringing it in. It's an interesting and potentially useful addition and it adds precisely zero weight.
The E-Tube software allows you to map the gears – deciding where the chain will go next when you upshift or downshift from any chainring/sprocket combination – in any way that you like.
You can take or leave all of this stuff. If you just want to stick with normal shifting, that's perfectly do-able.
The front derailleur is designed to work with outer chainrings from 50-tooth to 55-tooth and has a total capacity (the difference between the number of teeth on the two different chainrings) of 16 teeth, so it'll work fine with all of the most common road setups.
The front derailleur is a fairly compact design that's 10g lighter than the previous Di2 model.
Shifting is fast and smooth, even if you're shifting under power. It has performed perfectly throughout the review period without so much as a dropped chain. You still get auto-trimming, of course – where the front derailleur moves by itself to avoid chain rub as you shift across the cassette.
The rear derailleur has had a major overhaul, borrowing Shadow technology from Shimano's mountain bike groupsets so that it is positioned further below the functioning sprocket. In other words, it juts out less than previously, sitting more underneath the chainstay.
What's the point? The idea is that this results in a slimmer profile which improves aerodynamics and provides more protection from damage in the event of a crash. The Shadow design can also make wheel changes easier because the derailleur is moved further out of the way of the dropouts.
Shimano says that the design offers faster and more precise shifting than ever before. Well, it's certainly fast and precise, although I wouldn't say it's noticeably different from the shifting you got previously. That's not a criticism; once set up properly it works perfectly, never missing or even struggling when you find yourself needing to dump a few gears in a hurry.
The rear derailleur is designed to work with a maximum sprocket size of 30 teeth and a minimum of 11. The maximum difference in size between the front chainrings is 16 teeth and the total capacity (difference between the number of teeth on the two chainrings added to the difference between the number of teeth on the smallest and largest sprockets) is 35 teeth – so you can run a compact chainset (50/34t chainrings) with an 11-30 cassette, for example. There is just one cage length that covers all configurations.
Weight 621g (53/39-tooth, 170mm cranks)
This is the other component that has had a big revamp and Shimano has ended up with something that divides opinion in terms of looks. You can make your own mind up on that one.
The Hollowtech II chainset is anodised aluminium with a steel axle. The four-arm spider is hollow-forged and the cranks are chunkier than previously, although the overall weight is a smidge lower than before. Those cranks are asymmetric, the idea being to put the strength where it's most needed for the transfer of power, and the outer chainring has extra reinforcement.
Shimano has altered the design to work with disc brake road bikes (which generally have 135mm rear spacing) and shorter chainstays without increasing the Q-factor (the distance between your pedals) from 146mm.
The chainset is available with double chainrings only, in these options: 50/34t, 52/36t, 53/39t, 54/42t and 55/42t. As previously, they all have the same bolt circle diameter, 110mm, so you can switch between all chainrings on the same crankset. The time trial versions are a little more expensive at £529.99. They come in crank lengths from a diddy 165mm up to a whopping 180mm.
Shimano is also now offering its power meter chainset, although we'll run a separate review on that.
In use, the chainset feels as stiff as before despite the slight weight loss and having just a 24mm axle (as opposed to the 30mm aluminium axle you get on many systems these days). Shifting between chainrings is as crisp and reliable as ever. I've been using a 52/36t chainset – so there's a 16-tooth size difference between the chainrings, as there is with the 50/34t option – and moving from the inner to the outer has always been simple without any groaning or hesitation. It just happens quickly and effortlessly. Essentially, despite Shimano's changes to recognise the growing popularity of disc brake road bikes, the shifting is as good as ever.
Weight 175g (11-25-tooth)
The 11-speed cassette is available in five different versions: 11-25t, 11-28t, 11-30t, 12-25t and 12-28t.
The six smaller sprockets are nickel plated steel, the five larger ones are titanium, and the spider arms (why aren't they called spider legs?) are made from carbon.
The news here is that this is the first time a Dura-Ace cassette has been available with a 30-tooth sprocket. (The 11-30 cassette is £229.99). That'll please some people who want a lower gear for really steep hills, although you can't go to 32 teeth like you can with SRAM Red eTap.
If you swap from an 11-25t cassette to 11-30t, say, you'll need a longer chain but you won't need to swap your rear mech because that's a 'one size fits all' design.
Weight 148g (rear), 150g (front)
You can, of course, get Dura-Ace dual-pivot brake callipers (and hydraulic disc brakes, which have been brought into the groupset), I just happen to have been using a bike that takes direct mount brakes.
Both the direct mount and the dual-pivot versions are made from anodised aluminium with magnesium cartridge shoe holders, and they fit rims up to 28mm wide – up from 25mm on 9000 Series Dura-Ace. Shimano has obviously recognised that more and more people want to run wider tyres on the road these days, so extra clearance is needed even on a race-focused groupset like Dura-Ace.
Shimano claims a 43 per cent reduction in flex over previous Dura-Ace brakes. Do you notice that? Not me. The improvement might sound dramatic but if there's hardly any flex to start with, 43 per cent less doesn't make a whole lot of difference.
Braking has been one of Dura-Ace's biggest strengths in the past, and so it remains. These provide sure, linear stopping power that's highly predictable. They really are superb.
Weight 247g (114 links)
This chain has an asymmetric plate design for 11-speed, hollow pins and Shimano's Sil-Tec technology, which means it has PTFE plating on the inner and outer links and the rollers to promote smooth running and longevity.
In all honesty, I can't say I get too excited about chains. This one does its job, it moves quickly across sprockets when you ask it to, it's light and pretty durable... end of story.
Actually, it's not quite the end of the story. Shimano now – finally – offers a quick-link (SM-CN900-11) that makes tool-free assembly possible.
Shimano offers three different Dura-Ace bottom brackets: the threaded BB-R9100 (65g) and two press-fit models, BB92-41B (54g) and BB72-41B (63g), depending on the system your bike takes.
We've already reviewed the Shimano Dura-Ace R9100 SPD-SL pedals here.
As well as the key components listed above, you'll need various other parts for a Di2 system to function. Most notable of these is perhaps the new version of the junction box (£109.99), which plugs into one end of your handlebar, doing away with the need to have one hanging underneath the stem. It's very neat!
* Junction A box £99.99-£109.99
* Battery £139.99
* Internal junction £27.99
* Charger £99.99
* Wires £21.99-£24.99
Dual control levers (pair) £549.99
Front derailleur £329.99
Rear derailleur £549.99
Mechanical brakeset (pair) £319.98
Bottom bracket £49.99
Bar end Junction A box £109.99
Internal junction £27.99
E-Tube Wireless Unit (optional) £74.99
E-Tube wires £114.95
These are all at full recommended retail prices, of course. As we all know, you can find Dura-Ace Di2 considerably cheaper if you shop around.
That's considerably more than SRAM Red eTap, although eTap doesn't offer customisation of the electronic functions.
R9150 might not represent the most radical groupset overhaul ever, but it certainly moves Dura-Ace forward and brings it up to date in recognising the growing importance of wider tyres, larger sprockets and disc brakes in the road bike world. You might or might not be attracted by the Synchro Shift and semi-Synchro Shift options, but the ability to alter your Di2 setup via a consumer-focused phone app is certainly the sort of thing we've grown to expect these days. Oh, and it's very slightly lighter than before too.
You're certainly welcome to disagree – variety is the spice of life, right? – but to my mind Shimano Dura-Ace Di2 is the best road groupset out there right now. You might prefer the shift system of Campagnolo or SRAM (or FSA, come to that), and that's likely to influence your preference, but my view is that this is the one the others have to beat.
Excellent top-level groupset with superb shifting, powerful braking and plenty of scope for customisation
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road.cc test report
Make and model: Shimano Dura-Ace R9150 Di2
Size tested: 52/36 chainset, direct mount brakes
Tell us what the product is for
Dura-Ace is Shimano's top-level road groupset, focused on the requirements of racing (although you don't need to use it for racing, of course).
Shimano says, "System engineering at its peak. Each of the components magnifies the qualities of the others for an unparalleled level of performance. Optimising input to maximise output. That's how it achieves supremacy."
Tell us how the product performed overall when used for its designed purpose
It puts in a superb performance. To my mind, it's the best road groupset out there, although other people might have other preferences.
Tell us what you particularly liked about the product
The shifting performance is excellent and so is the braking.
Tell us what you particularly disliked about the product
It's a shame you have to pay this much, but it is professional-level kit.
Did you enjoy using the product? Yes
Would you consider buying the product? Yes
Would you recommend the product to a friend? Yes
Use this box to explain your overall score
Pretty much everything about Dura-Ace Di2 is exceptionally good. Yes, it's expensive, but top-level groupsets always are. There's no way the price tag should pull the overall score down below 9.
About the tester
I usually ride: My best bike is:
I've been riding for: Over 20 years I ride: Most days I would class myself as: Expert
I regularly do the following types of riding: commuting, club rides, sportives, general fitness riding
Mat has been in cycling media since 1996, on titles including BikeRadar, Total Bike, Total Mountain Bike, What Mountain Bike and Mountain Biking UK, and he has been editor of 220 Triathlon and Cycling Plus. Mat has been road.cc technical editor for over a decade, testing bikes, fettling the latest kit, and trying out the most up-to-the-minute clothing. We send him off around the world to get all the news from launches and shows too. He has won his category in Ironman UK 70.3 and finished on the podium in both marathons he has run. Mat is a Cambridge graduate who did a post-grad in magazine journalism, and he is a winner of the Cycling Media Award for Specialist Online Writer. Now over 50, he's riding road and gravel bikes most days for fun and fitness rather than training for competitions.