Shimano GRX Di2 2x12 Speed Gruppo + Wheels

When Shimano launched 12-speed GRX – the blue brand’s gravel specific moniker – it came with all the marketing lingo you’d expect. Everything from gearing options to the hoods' ‘ribbed surface texture’ has been ‘optimized’ for gravel. Chain management has been improved, and the words “clearance”, “aerodynamics”, and “flared” feature regularly.

At its technological heart, the new GRX system rolls around on HYPERGLIDE+ (HG+) with a SHADOW RD+ clutch-equipped derailleur, shifting 12 rear gears, through a “semi-wireless” configuration. This lack of cockpit wiring is probably the most noticeable change over the previous GRX. It comes in an array of 1x, 2x, mechanical, and battery-equipped Di2 options. Notably, if you want to go Shimano electronic and want gear range, your only current option is the 2x system. If you’re looking for a wide range 1x setup you’ll have to shop elsewhere or wait until Shimano finally drops the long-awaited, rumoured-to-be-fully-wireless new XTR Di2 group to play mix & match.

For review, I’ve got a full 2x Di2 gruppo: brifters, rear derailleur, cassette, crankset, and yes… a front derailleur. It’s been 8 years since NSMB reviewed a 2x drivetrain; the XTR Di2 and portmanteau equipped “Thundervolt” was likely the last 2x bike seen on NSMB until the Canyon Grizl, a bike I reviewed and almost immediately converted to wide range 1x11 speed and complained about the lack of gear resolution.

To pair with the 2x12-speed Di2 gruppo, Shimano included the also-new GRX wheelset. The carbon WH-RX880 hoops are held together with 24 spokes and come with the 2024 requirement of “gravel-optimized aerodynamics”.

I don’t have thousands of kilometers aboard the gruppo or wheels yet, but I’ve mounted them all to the Kona Ouroboros as a test mule, and have some impressions through installation and setup, as well as a bit of initial riding.

Groupset Options & Hardware

Shimano launched three 12-speed GRX groups in the fall of 2023 – two 1x options, and a 2x. Battery afficionados would have to wait until May 2024 for Di2 to arrive, available solely in 2x, but with a couple bits to mix and match for gearing. As you'd hope given the shared semi-wireless architecture and other components, you can mix and match with pieces from Shimano's road line as well. As long as they're the current generation you can choose which brifters you prefer, and whether or not you want a clutch. Take note the crankset chainline is +2.5mm more outboard on GRX for tire clearance, so you'll need to ensure you have a matching front derailleur.

As of writing, there's no way to mix in mountain bike cassettes and rear derailleurs. Mountain Di2 still relies on the earlier fully-wired configuration with junction boxes. Without spoiling too much of this review, that's probably the drivetrain I'd be gunning for if I were building a Shimano gravel bike: a 'mullet' configuration with road crankset and brifters paired with a wide range mountain rear derailleur.

Is 2025 the year we'll finally see an update to XTR Di2? Will it be fully wireless? Only time will tell.

Let’s have a look at the various components that make up the review gruppo.

Disclaimer

I’ve been using SRAM AXS components on most of my bikes for a long time. I’m very comfortable with the AXS app, connecting hardware, and I’ve done everything from firmware updates to determining chain length heaps of times. And if I have trouble, I have friends at SRAM I can directly annoy with questions. Despite Shimano launching Di2 into the drop bar world a whopping fifteen years ago and a full decade of Di2 in the mountain bike realm, I’ve never ridden it or used the software. Why I mention this is it’s been a learning process for me; I’ve struggled with some bits of the installation, been very confused by the app, but it’s very likely that some of my frustrations of challenges are just a function of me being integrated into another system.

Think of it this way; I’m also a long-time Android user, and if you threw me a Blackberry the first time I needed to change the lock screen I’d probably get frustrated. Now that setup is complete, and I have enough knowledge to adjust things on the fly instead of needing to Google-search, everything on the software front is improving.

Software

I know, I know. Some of you are horrified we have to have a software section. But it's an important part of the experience for modern electronic drivetrains, and functionality and user experience here is important, especially with a front derailleur. It's also a mandatory part of initial setup if you're not having your local bike shop do your installation, and even then, there's some fiddling and setup changes you may want to make with your new investment that'll require the gracefully named E-Tube Project Cylist app.

Overall, I've found E-Tube to be somewhat confusing and complicated. And while some of that is absolutely me (see above disclaimer), the mark of a good app is a user interface that doesn't require experience and is intuitive to use on the first time. Talking to a couple of full-time wrenches, the consensus was that while most of the apps (SRAM, Bosch, Shimano) have their issues, Shimano's is "not easy to navigate" and " they bring a legacy hardware development mindset to [software] development." Using the Android/Blackberry analogy above, if you tossed me an iPhone I'd bet it wouldn't take long to get up to speed, as Apple spends inordinate amounts of time and money ensuring the user experience feels innate.

As an example, it took me an embarrassingly long amount of time to figure out why my fully-synchronized shifting wasn't working. You can set shift points in the app for your front derailleur (and how many gears you'd like to change simultaneously in the rear), but I was only ever getting manual mode, despite 'applying changes' in the app. As it turns out, you have to double tap the hardware button on the rear derailleur, and know what colour and combination of blinking LED light indicates which mode you're in. While simple enough now that I'm aware, it's not the most straightforward process.

All that said, now that I'm somewhat accustomed to the flow of E-Tube it's certainly workable, and it's not something users should need to use frequently after everything is set up. There's an enormous amount of functionality within the app, shift speeds, shift points, you name it. Other than brifter firmware updates (which requires a cable and the 'Professional' version of E-Tube), if there's something you want to change about how your drivetrain reacts to button presses you can probably tweak it in E-Tube.

Cost and Weight

None of these parts come particularly cheap - after all this is the top of the line for Shimano's gravel lineup. All in, if you're going for a new build and not carrying anything over, you're looking at somewhere in the neighborhood of $3,400 after all the rotors, wiring, and the like. While certainly an eyewatering price tag, this is a couple hundred dollars cheaper than Big Red's recently released full-mount 1x13-speed SRAM Red XPLR group. It's also a big number as it's not how we mountain bikers are used to building bikes, ordinarily separating out various components to mix and match brakes, cranksets, and drivetrain - that $3,400 figure is all-in.

Riding Impressions

I'm working on logging enough mileage on this drivetrain to speak confidently about it. Given Shimano's history, I don't have any serious durability or longevity concerns.* My first rides were a bit of faff. There was a lot of stop/start as I learned to efficiently navigate E-Tube to adjust shift points and behaviour. I'm also unable to really take advantage of all the buttons available as I use a Hammerhead computer; after SRAM's acquisition of the brand Shimano (somewhat understandably) requested they remove support for Di2. This doesn't have any real impact on riding, but if you're a real data nerd it's something to take note of. I also wish I could assign one of those buttons to a dropper post, but sadly there's nothing compatible - and before you ask, it's a different wireless protocol than the new Fox post.

*Well, ok. We'll keep an eye on the crankset.

Shifting is what we've all come to expect from Shimano Hyperglide+: solid. Shifts are quick and precise, and while not as smooth as SRAM T-Type, they're faster. So far, even with fully synchronized shifting, I'm not sold on having a front derailleur again. Sure, gear resolution is nice, but I'm not convinced this is the appropriate place on the gear range/gear resolution spectrum for me. I'll do some more back to back with SRAM Red XPLR to compare shift speed and quality, and we'll think hard about range and resolution for the full review.

Chain retention has been good so far - although I haven't fully explored the "limits" of what the Ouroboros can do with the new drivetrain, so we'll see how it does on some real mtb-lite trails and whether or not it can keep everything engaged across multiple chainrings. There's enough tension in the clutch to keep everything relatively quiet, however given the electronic actuation I'd like to see a little more tension (in a mechanical system this can impact the force required for downshifts with your thumb, this isn't the case here).

The hood shape is comfortable, and the brake levers themselves are well positioned for flared bars, taking little effort to pull. This was somewhere the previous GRX excelled as well, and the small revisions in the move to 12-speed haven't dampened performance.

I'm looking forward to thrashing this around in the wet and muddy conditions to come here, thus far the worst conditions that've been thrown at the gruppo are all moon-dust related. I'll keep you updated, after we log some more miles!

Shimano GRX Di2 2x12 Speed Gruppo