Shimano Ultegra R8170 Di2 Disc Groupset

The new Shimano Ultegra R8170 Di2 Disc groupset really closes the gap to Dura-Ace. Unless you particularly want to spend more, or need to save that little bit of weight, there is no point in looking past Ultegra R8170. The shifting is smoother across the cassette than previously, and the brakes have improved too. It is just brilliant.

Over the years, Shimano's second-tier groupset has been providing the majority of the performance of the top-tier Dura-Ace groupset, but at a significantly reduced price. That's thanks to less expensive materials, at the cost of a few hundred grams extra weight.

But with the latest R8170 groupset, Shimano has closed the performance gap to the point of undetectability. There is no discernible difference between Ultegra and Dura-Ace. So, unless you particularly want to dip your hand deeper into your pocket, or you need to save a tiny bit of weight, there is absolutely no sensible reason to buy Dura-Ace – Ultegra R8170 is just as good.

The new groupset rides largely like the old one. If you buy it on a complete bike you won't notice the lack of wiring between the shifters and the seatpost-mounted battery, but if you're upgrading it will save a few seconds of wiring.

The lack of wires has absolutely no negative effect on ride feel, and that should be heartily applauded. Shimano has absolutely smashed it out of the park when it comes to shift quality. Where SRAM's eTap has always felt clunky – too clunky, in my opinion, for such a high-end groupset – Shimano's latest Di2 feels smoother and faster than before. And let's be honest, Shimano is improving on shifting quality that was already absolutely fantastic, so to feel an improvement is very impressive.

When it comes to braking I can again see improvements. Shimano has fixed the major issue with the R8000 brakes, so now, after you've thoroughly heated up the brakes with a long period of heavy braking, you can let them off and suffer no noise whatsoever. It is a blissful silence that I'm pleased to say has stuck around for the entire test period.

At this level it's worth making sure everything is right, though; prior to having the groupset installed, I had my brake mount surfaces faced, and I can't stress enough how crucial this is. While the front was fine on my frameset, the rear had one surface a whole 0.9mm lower than the other. That might sound tiny, but it is more than enough to cause headaches as you try to set up your brakes.

The new brakes also have the progressive feel you'll find on Shimano's GRX gravel groupset. The lever/pad relationship is not linear; you get lots of pad travel at first (to bring them in from a decent clearance) and then far less as you pull harder on the brakes (for easy, smooth modulation). The feel in the hands is lovely, with plenty of control for scrubbing speed into corners and loads of power if you need to stop quickly.

I really like the feel of the new levers, too, and the hood shape is very comfortable. The inward tilt of the shifter body feels very natural, and the smooth lines at the front of the levers are great for all-day comfort.

Design changes

Two things have happened here that have really improved performance. First, you'll find 10 per cent extra clearance at the pads. And second, the ServoWave design improves the progression of power through the lever stroke. These two measures have worked brilliantly, creating brakes that are powerful, easy to control and quiet.

Take the pads out and you find what appear to be different pistons. If they stick less over the longterm I'll be happy, but frustratingly Shimano has made them black, so it's hard to see brake dust when you're cleaning them.

For the once-per-year occasion when you need to bleed the brakes, the bleed port has been moved to the side of the calliper, allowing much easier access in tight rear triangles. You won't need a spanner any more either, as the port now uses a hex key. It is a much cleaner design, though I have already lost one of the bleed port covers.

And finally, rejoice! The only flathead screw (it held the pads in) has been changed to an Allen bolt. That should reduce the number that need to be drilled out, but you should still use an anti-seize compound just to be safe.

Shifters

In terms of groupsets, there are few parts that leave an impression like shifters. This is where your hands are going to rest for the majority of a ride. You'll be in contact with them every time you change gear or brake, and if they feel bad it can be incredibly annoying.

Shimano's Ultegra R8170 shifters have (like Dura-Ace) become longer, taller and fatter. Shimano says it's due feedback from the pros, but I suspect that these needing a CR1632 coin cell battery in each shifter also played a role in the increase.

With my medium-sized hands I found the new shifters very comfortable, with a secure grip on bumpy roads. Shimano has increased the length of the shifter body to enable you to loop three fingers under the shifter easily.

The button profiles have been altered and are now very pronounced. I have to say I had very few issues with the old levers while wearing gloves anyway, but with the new levers the situation is even better. Up at the top of the shifters you find some extra buttons. I have mine set so the right side starts a new lap with a double press, and single presses change my Garmin screen. It's all very easy to use.

As with the old model, there is plenty of free-stroke and position adjustment so that you can physically tune the levers to your hands.

Rear derailleur

Where you used to have a choice between an SS (short) cage and a GS (medium) cage derailleur, you've now just got the GS option. Shimano has evidently seen that most people (even the pros) use wide-range road cassettes these days, and has sensibly reduced the number of parts it needs to produce.

But you probably don't care about Shimano's production lines, so let's talk about how smooth this new derailleur is. This, rather than the speed or power, is the noticeable thing with the R8170 rear derailleur. Shift under full power while you're cross-chaining in the big ring and trying to chase an attack on a climb, and it simply pops you into the gear you've asked for. It does this quickly and quietly.

The functionality of the old Junction A box has moved to within the rear derailleur too, and while this is great for integration, I have a few reservations about making the most exposed part of the groupset even more complicated – and therefore even more expensive to replace in the event of a heavy crash.

It also means that on-the-fly gear adjustments are out of the question. It's a minor thing, though, when the improved integration brings out-of-the-box connectivity to Shimano's eTube app.

The internals

Internally you'll find the same motors and hardware as the more expensive Dura-Ace, with the cost and weight differences coming from the less fancy materials for the outer casing.

The motors are now stronger, too, which goes a long way to providing the claimed shift speed increase. Finally, there is a new charging cable which clips easily onto the port.

Front derailleur

The story is similar when you move to the front derailleur. Shimano made noises about an increase in the speed of the shift but, quite honestly, I believe the differences I can feel are due to the derailleur becoming more powerful. It really shoves the chain between rings now, which – provided your indexing and limits are set correctly – results in lightning-quick shifts, even under load.

The limit screws have now entirely disappeared from the front derailleur. You're left with just a single support screw, with the method for indexing the gears now also being used to set the derailleur limits. It is a bit more of a faff to set the limits now because you have to keep entering and exiting adjustment mode, but at least there are no tiny limit screws to round off.

Cassette

The cassette is 12-speed and only available in two options; 11-30t and 11-34t. Combining the former with 52/36t chainrings has given me a gear for pretty much every situation. Shifts are smooth across the whole cassette, and the new 12th sprocket occupies the 16t space. That's ideal for faster flat rides, and I've even found it useful for those faster climbs when you're in the little ring but quite a way down the block. It just evens out cadence changes, which is never a bad thing.

What I really like are the single-tooth jumps for the first seven sprockets of the 11-30t cassette, as the result is the feeling you have the perfect gear at all times on the flat.

> Which chainset is right for you? Should you choose a standard, a compact or something else?

And before we leave the cassette, it is time for everyone to say thank you to Shimano. Yes, this uses a new spline pattern, but it's backwards-compatible with 11-speed Shimano freehubs. You won't have to go out and buy a new wheelset to upgrade to R8170.

Incidentally, we also have the Ultegra C50 wheels on test, but they will be reviewed separately.

Chainset

Another noticeable change comes at the chainset, which gets a much more symmetrical crank design. While it is a small change to the aesthetics (now much chunkier than before) the real benefit will be felt by third-party power meter brands such as 4iiii and Stages. The increased symmetry in the drive-side crank should make getting balanced and accurate data a bit easier.

We're yet to get our hands on the Ultegra R8100-P power meter, but will have an in-depth review when we do.

You might have seen a few reports of Shimano HollowTech II cranks failing, with the bond between the two parts of the drive-side crank usually being the issue. It seems that water was causing corrosion in the bond, possibly after entering via the hollow axle. It's something Shimano says it has addressed with the new cranks, placing a plastic plug inside the axle to keep water out.

> Get your gears shifting sweetly: How to tune a rear derailleur

While it will take several thousand miles to determine the success of these changes, what I can comment on is the shifting performance. The chain moves between the 36t and 52t chainrings incredibly efficiently, and with very little noise. Shimano's chainrings have offered excellent shifting for years, and they continue to do so.

One thing I'm sad to see go, though, is the racer's chainring combination of 53/39t. The 52/36t combo is now the largest available with Ultegra; if you want the 54/40t that has replaced the 53/39t, you'll have to step up to Dura-Ace.

You still get the option of 165mm, 170mm, 172.5mm or 175mm crank lengths.

Chain

Here Shimano has switched to its 12-speed mountain bike chains. This is the XT chain, which is claimed to be a bit quieter than before thanks to chamfered edges, though in my experience drivetrain noise mostly comes down to the chain lube you use anyway.

The app

As I've mentioned, you've now got Bluetooth connectivity built into the groupset, rather than having to buy the separate D-Fly unit for a silly amount of money.

The app is easy to use and connected me to my gears in minutes. From here you can associate the groupset with a specific bike – useful if you're going to be connecting several other bikes – and make all sorts of useful tweaks. You can switch between shift modes from classic manual to having the front derailleur handled for you, for instance, mess around with which shift button does what, or alter the shifting speed.

Value

The price for the Ultegra R8170 groupset is a little tricky to pin down, but we believe the RRP is £2,399; up from £1,999 for the R8070. That isn't too horrific an increase, and given the improvements across the groupset, I'd be happy to spend my money on it.

Overall

I think Shimano has produced a fabulous Ultegra groupset that delivers perfect performance. Now, more than ever before, there really is no point in the vast majority of us paying more for Dura-Ace.

Verdict

Fast shifting and brilliant brakes, now on a level with Dura-Ace – but cheaper