Review: Shimano 105 R7100 Di2 Groupset

Shimano’s 105 R7100 Di2 brings semi-wireless electronic shifting to its mid-level groupset, and an extra sprocket to boot, bringing it into line with range toppers Dura-Ace and Ultegra. Some will mourn the lack of a rim brake option, but if you are happy to embrace some of the best performing hydraulic braking power and electronic shifting on the market, this is probably the most cost-effective of all the higher end Shimano road bike groupsets. It’s pushed hard on price by its main ‘Rival’, though.

So, it’s happened – 105 has gone fully electronic and 12 speed; there is no mention of a mechanical shifting option, and the rim brakes have been chucked in the bin.

In some ways I wish that wasn’t the case – the option of a 12-speed mechanical groupset for those who want Shimano but don’t want electronic is a gap that could do with filling, and I’m still a big fan of quality rim brakes.

I can understand why Shimano has gone down this route, though – sourcing a new frame a few months ago to be built up with a rim brake groupset highlighted how much the market is shrinking as manufacturers continue the shift towards disc brakes.

Enough about what we haven’t got, though, let’s talk about all the goodies that we do!

In use

I’ll go through each of the components and options piece by piece in a bit, but first I’ll give you the lowdown on what 105 R7100 is like to use.

Brilliant, basically. I’ve spent time on all of Shimano’s Di2 groupsets right from the first iteration Dura-Ace up to the present models, and while early releases saw big jumps in performance and usability, the recent couple of updates of Ultegra and Dura-Ace have been more about refining the quality from the previous model, and that’s the point where 105 joins the throng.

Shimano has taken the technology, ergonomics and quality of Dura-Ace R9200 and Ultegra R8170 to deliver what is an electronic groupset for those on a tighter budget.

While shifting quality and braking is important, comfort and ease of interaction with the STI units is probably the most crucial. After all, you aren’t changing gear all of the time, but you will be riding on the hoods for many, many miles.

The 105 shifter units are identical in shape to the Ultegra and Dura-Ace offerings, with large buttons that fall naturally to the fingers even if you are switching between Shimano’s mechanical and Di2 groupsets.

With the brake reservoir, but without any mechanical components for the gear changes, Shimano has managed to create an STI unit that mimics its mechanical rim brake offerings for size, meaning less bulk than SRAM’s units by a small amount.

I find the design very comfortable, with a rubber hood cover that is soft to the touch and grippy to stop your hands slipping when wet.

The curve of the brake lever allows your fingers to settle naturally in position, and thanks to the power of the hydraulic system, you can brake heavily using just two fingers. Unless you were using it all of the time, the early Di2 units took a bit of thinking about where your fingers needed to be to shift, especially when wearing gloves. These new units don’t have that, everything just feels naturally positioned and I never fluffed a shift.

When it comes to the shifting, the click of the buttons is light – lighter than that found on SRAM’s AXS and Campagnolo’s EPS models – but it isn’t so light that you lose the feel of the shift. There is a positive click there and that is replicated by the front and rear mech; Di2 still keeps you connected to the system like a mechanical groupset, but with a much lighter and quicker action.

To test shifting under load, I’d hit my local 20 per cent climb in the big ring before dropping into the small ring when my cadence had dropped to around the 30rpm mark, and while anyone with even an ounce of mechanical sympathy will wince at the thought of shifting a chain across chainrings at this point, 105 doesn’t share your concerns.

The shift was dealt with without issue, and it’s the same at the rear. A big help is that you can just hold a button on the shifter and the mech will make continuous shifts in either direction.

Overall, in terms of performance of both the shifting and braking, the R7100 Di2 groupset can barely be faulted, and the STI units are some of the most comfortable on the market.

Shifting/Brake Lever – ST-R7170

£349.99 (including shifters and brake calipers/hose kit)
Weight: 423g (pair)

Just like Ultegra and Dura-Ace, the 105 shifters are wireless, something that’s only been available on the latest iterations to bring them in line with SRAM.

SRAM, though, offers a fully wireless system where its derailleurs use their own batteries, and everything is controlled via Wi-Fi.

The R7170 shifters use two CR1632 coin batteries for their power supply which Shimano says will last three-and-a-half to four years. The mechs are then connected to the main battery via wires.

Straight out of the box, the shifter buttons have the same functions as all Di2 units, but they can be customised using the E-TUBE app; this will also sort out firmware updates.

One thing Shimano hasn’t offered are ports for ‘sprinter shifters’ which you can attach to the handlebar around the drops for when you can’t reach the levers.

Chainset – FC-R7100

£169.99 FC-R7100/£119.99 FC-RS520 
Weight: 766g (FC-R7100)
(Non-series FC-RS520 12-speed is also compatible)

For this 105 series the pro-level 53/39T chainset isn’t offered here, with the two options being 50/34T and 52/36T.

For the type of riders likely to be using 105 I’d say that’s a fair shout, with both options offering a great spread of gears high and low end for those who are racing or just riding.

I must admit I do like SRAM’s idea of smaller chainrings paired to a wide-ranging cassette as found on its latest Rival AXS eTap groupset. It feels efficient to me, barely having to drop down from the large chainring until hitting the steepest of climbs. There are trade-offs with the SRAM cassette sizes, though, but more about that in a minute.

Design-wise the R7100 unit has a new look over the previous R7000 crankset, although it still maintains the four-arm attachment to the chainrings with a 110mm bolt circle diameter (BCD).

Using Shimano’s Hollowtech II design, the aluminium alloy cranks are formed hollow to keep weight down, and they certainly aren’t lacking in stiffness.

Unlike SRAM, though, Shimano doesn’t offer any power meter options.

Crank lengths are the typical 160, 165, 170, 172.5 and 175mm, and Shimano has retained the 24mm diameter axle, resisting the urge to increase to 30mm like many brands.

Shifting between the chainrings is great even under load thanks to the design of the various ramps and tooth profiles.

Front Derailleur – FD-R7150

£149.99
Weight: 142g

While many of the components of this new 105 groupset look much the same as the latest Ultegra, the front mech looks more similar to previous Di2 versions, being bulkier than the new units.

I’ve got test bikes that are running the latest Ultegra Di2, so I’ve been able to run the groupsets side by side.

For me, the front mech is the only real noticeable difference in terms of performance between the two. Ultegra’s shifting is just a tiny bit faster; no cleaner or crisper, just quicker.

That isn’t to say the 105 unit is sluggish – far from it! – it’s just that I’m highlighting where savings have been made.

Shifting from the front mech is great, with plenty of power to move the chain even under heavy load, and the automatic trimming mode works as well as always, tweaking the chainline as you move up and down the cassette.

The maximum chainring size it can cope with is 52T, and a range of 16 teeth (the difference between big and small chainring).

Rear Derailleur – RD-R7150

£274.99
Weight: 302g

The 105 rear mech looks very similar to the Ultegra version but has a longer cage to cope with a 36T sprocket.

According to Shimano this is the brains and hub of the Di2 unit, incorporating the charging port, adjustment switches and everything else. While it uses Shimano’s Shadow technology, which sits the mech underneath the cassette in a bid to keep it out of the way, should you crash it’s still going to be one of the most vulnerable components, and pricey to replace.

It’s good at doing its job, though: gear changes are quick and precise, plus setting it up is simple too.

Cassette

£69.99 (11-34T), £89.99 (11-36T)
Weight: 361g (11-34T)
Options: CS-R7100-12 – 11-34T; CS-HG710-12 – 11-36T

Cassette-wise, as you can see there are just two options of 11-34 and 11-36.

Personally, I’d like to see more – 105 has always been seen as a groupset that covers all bases, capable of everything from touring to racing, so it would be good to see some closer ratio options such as an 11-25 or 11-28.

SRAM’s 12-speed cassettes offer a 10T sprocket which works with its smaller chainrings to still give a large gear ratio. To create the wide-ranging ratios, though, they do tend to have large jumps at the upper end of the cassette, something that Shimano doesn’t suffer from.

The 11-34T goes: 11, 12, 13, 14, 15, 17, 19, 21, 24, 27, 30, 34.

Shimano has stuck with the 11-tooth smallest sprocket so as to make the groupset compatible with 11-speed freehub-equipped wheels.

Brakes – Calipers (BR-R7170), Rotors (SM-RT64)

£26.99 per rotor
Weight: Rotors – 286g per pair (callipers included with shifters)

To look at, the 105 calliper hasn’t really changed much over previous versions, but Shimano has now added 10 per cent more pad clearance to minimise brake rub and alignment issues.

To be honest, I never really had an issue with earlier models, but this does at least give more tolerance for setup.

The SM-RT64 rotors are available in 140, 160, 180, 203 and 220mm diameters, although only the smaller sizes are really needed for road use.

They don’t quite have the cool looks of the RT-CL800 models used in the Ultegra groupset, but performance is still great – powerful and with loads of feel at the brake lever.

Chain – CN-M7100

£34.99
Weight: 252g

The chain selected for the 105 groupset is from the mountain bike SLX line-up. It comes with a quick-link assembly and SIL-TEC treatment which Shimano claims gives extended off-road durability. Ideal if you are going to be using 105 as an all-year-round groupset.

Value

The majority of riders using 105 Di2 will have had it come as part of bike package, but if you are going to buy it as a groupset for your own build, with all of the bits and pieces that you are going to need like wires, batteries and so on, it’s going to set you back £1,730.

That’s a saving of more than £669 over Ultegra (more, in fact, as you’ll need to add rotors because they aren’t included in the Ultegra price).

The SRAM Rival eTap AXS groupset that we tested comes in at just £1,470 with power meter, £1,268 without, which is a massive saving. Even SRAM Force, the next level up, comes in cheaper at £1,540.

For once, Shimano 105 isn’t really looking like the affordable groupset it once was.

Conclusion

In terms of its performance and rider integration, I can’t fault 105 Di2. It’s a great groupset and looks awesome too, with its gloss black finish. I can’t help feeling it’s a shame that the upgrades haven’t been brought across with a mechanical groupset, but hey, that’s the future I suppose.

It isn’t as good value as its main rival, though. Prices for fully built bikes with Rival eTap and 105 Di2 aren’t that different, but buying a groupset for your own build, at full RRP, SRAM offers better value for money over Shimano.

Verdict

Excellent performance, but not the most competitive price-wise