Shimano Launches 12-Speed GRX Di2...and its 2x Only
Takeaway: Shimano’s refresh of the GRX Di2 electronic gravel groupset shifts well, stops great, and doesn’t weigh too much. And it is priced on par with its main rival, SRAM’s Force AXS. However, while its performance is fine, the new GRX Di2 group does not make you go “wow.” It looks and feels dated. The group’s lack of 1x drivetrain options will leave many gravel enthusiasts scratching their heads.
The good news?
After a long wait, a new Shimano GRX Di2 group is here.
The bad news?
It’s only offered with two chainrings.
When Shimano launched its updated GRX 12-speed mechanical components nine months ago, the brand was transparent that an updated GRX Di2 gravel group was imminent. That was an unexpected position from the usually tight-lipped Japanese bicycle component behemoth.
Shimano’s gravel and road brand manager Nick Legan was similarly candid during his presentation on the new 2x12-speed GRX Di2 at an invitation-only launch event last week. Legan assured the assembled cycling media that Shimano would launch a 1x GRX Di2 variant in the future, though he could not provide any details about features, nor an expected launch date.
So, if you’re strictly a 1x drivetrain rider, you might want to read up on a new group with a 1x option instead of scrolling any further. But if you’re a fan of double chainring cranks and front derailleurs, sit down, grab the beverage of your choice, and let’s learn about Shimano’s latest electronic shifting gravel components.
What is New About GRX Di2?
GRX Di2 12-speed isn’t completely new from tip-to-tail. Instead, it’s a combination of parts that debuted last summer with the GRX mechanical 12-speed launch (RX820 series cranks and brakes) and a selection of new GRX Di2 products (RX825 series levers and derailleurs). Thus, if you own a 2x12 mechanical GRX bike you can upgrade to an electronic-shifting drivetrain with only a few components (plus, some wires and a battery).
I rode the new GRX Di2 group on a fully custom titanium-frame (and fork) Firefly Gravel bike. I used the bike for rides at Shimano’s media event and Stetina’s Paydirt gravel race in Carson City, Nevada, as well as riding near Bicycling’s headquarters in Easton, Pennsylvania. Overall, the group shifts smoothly (front and rear) and the brakes have good modulation and plenty of available power.
There are not many functional differences between the new GRX Di2 12-speed and elements of Shimano’s other 12-speed Di2 drop bar groupsets, the previous generation GRX Di2 11-speed, and the current GRX mechanical 12-speed. If you have ridden any of these component groups, you will already have a pretty good idea of how GRX RX825 operates.
Shift Levers (ST-RX825)
The new Di2 GRX levers are similar in appearance to the previous generation 11-speed GRX RX815 units with some improvements in function. Like their mechanical counterparts, the new electronic shifters use a raised hood design for better grip off-road and a mounting bracket optimized for use with flared bars. Similar to the RX815 levers, the new RX825 lever blades feature an anti-slip texture (Shimano claims it is updated for improved abrasion resistance).
Unlike GRX RX815, the new RX825 series is semi-wireless. Adopting the technology used in the latest generation Shimano Dura-Ace, Ultegra, and 105 Di2 road groups, the new GRX Di2 has wireless shifters paired to derailleurs wired to a central battery. Launched almost three years ago, the system works flawlessly and is generally easy to set up and adjust. And like the 105 Di2 levers, the RX825 units are powered by two coin cell batteries for extended service life.
Shimano also updated the levers’ accessory button (located on the inside of the pommels). This bonus button can control computer functions, set (via Shimano’s E-Tube app) as another shift button, or even adjust power settings on some e-bike motors. You can also assign different functions to short and long pushes of the accessory button.
Launching alongside RX825 is firmware—dubbed Front Shift Next—that changes the front derailleur with a tap of the same button (previous Di2 systems required assigning up and down shift functions to dedicated buttons). This firmware is stock on RX825 shifters but can be applied to any 12-speed Shimano Di2 system with an update at Shimano dealers.
The braking function of the RX825 levers is top-notch. The lever blades are easy to reach from the hoods or in the drops. Compared to Dura-Ace or Ultegra levers, the GRX levers have a higher pivot point to provide better power when braking from the hoods (where you spend most of your time when riding gravel). If you own a 12-speed Dura-Ace, Ultegra, or 105 Di2 bike and are unhappy with the hood shape, check out the GRX Di2 lever. They might be a better shape for some riders’ hands.
Derailleurs (RD-RX825 and FD-RX825)
The new GRX Di2 rear derailleur has the most visible stylistic changes of the group’s components. While its predecessor looked somewhat bulky and derived from Shimano’s 11-speed Deore XT Di2 mountain bike derailleur, the RX825 follows a cleaner form factor (though it still looks bigger than a Di2 road RD).
As on the 12-speed Di2 road groups, the rear derailleur serves as GRX Di2 12-speed’s electronic hub. It’s wired to the front derailleur via the battery and wirelessly communicates to the shift levers at the bar. The RD-RX825 is compatible with up to 36-tooth rear cogs and it also features a clutch for improved chain retention over bumpy terrain.
The groupset’s RX825 front derailleur is, essentially, the same as the RX815 changer with some refinements for the 12-speed system. Unlike the Dura-Ace and Ultegra front derailleurs that adopted a slimmer profile when they moved to 12-speed, the new GRX Di2 FD uses the older design and styling. Since the FD-RX825 is positioned outboard 2.5mm for added tire and mud clearance, it is only compatible with GRX 2x12 cranksets. The maximum ring capacity is 48 teeth and the derailleur manages a 17-tooth difference in front ring sizes.
Pricing, Weights, and Availability
The 12-speed GRX Di2 parts are available now through Shimano dealers. Retail prices and claimed weights (in grams) for the main components are below:
Shifters/Brakes
ST-RX825 and BR-RX820 (with pads and hoses) — $557, 415g (per side)
Crank
FC-RX820 (with 48/31T and 170mm, 172.5mm, or 175mm arms) — $250, 721g
Rear Derailleur
RD-RX825 — $410, 310g
Front Derailleur
FD-RX825 — $210, 142g
Total Group (including cassette, chain, rotors, battery, wires) — $2,534, 2,937g
Thoughts on the New GRX Di2
As I remarked in the opening line of my GRX mechanical review last August, “New GRX is completely adequate.” And the same rings true for the new GRX Di2. The RX825 12-speed electronic group functions very well, but it did not blow me away.
The derailleurs shift smoothly; the brakes are powerful and modulate well. But GRX RX825 does not have style and flair—it feels utilitarian and basic, not high-tech or cutting-edge.
And GRX Di2 feels incomplete and several years behind trends. The gearing options and refinements that I would expect from a top-tier electronic groupset for gravel riding and racing in 2024 are not there. Besides the obvious lack of a single-ring crankset and wide-range cassette, the group does not have power meter options (in the absence of a Shimano power meter, 4iiii is your best bet) nor can it activate a dropper post from the levers. These are key features of a modern gravel group.
When questioned about the lack of 1x options for the new GRX Di2, Shimano claimed that 2x systems are more popular than 1x on the other side of the Atlantic. Based on my prior experience in global product management for bike brands, I do not doubt the truth of this response.
But that doesn’t remove the disappointment for gravel riders and racers who prefer 1x drivetrains—or own 1x specific frames—and want to use Shimano components. Gravel grew from a niche subset to a legitimate bicycle segment and riding discipline within a decade. Shimano was early-ish to the party when it launched the first GRX groups in 2019, but that was 5 years ago—the gravel market is quickly evolving.
SRAM has the upper hand on the gravel drivetrain market for 1x, gearing options, and component compatibility. The brand offers 1x and 2x chainrings across all except the lowest tier of its four electronic drop bar groups, and each of those groups has power meter crank options. SRAM offers multiple cassette sizes for its drivetrains, an XPLR collection of wide-range 1x cassettes and rear derailleurs, and SRAM’s Eagle AXS 1X mountain bike derailleurs can pair with AXS drop bar shifters (AKA a mullet drivetrain) to provide even more gear range for gravel riding. Additionally, RockShox’s Reverb AXS wireless dropper works with AXS shift levers.
Hopefully, the updates Shimano has planned for its 1x12 GRX Di2 group will arrive sooner than later: The group needs more features and options to keep pace with SRAM. Shimano’s recall of more than 3/4 of a million cranks last year damaged its strong reputation for reliability. Perhaps some of the wireless derailleur and brake technologies recently uncovered in Shimano patent filings will find their way into the next generation of GRX and Shimano can regain some equity with gravel riders.
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