Shimano GRX Di2 - the most important facts in brief
Shimano is doing a lot of things right with the new GRX Di2. It is technically state-of-the-art and functionally flawless. However, the groupset does not set new trends for gravel bikes, as one might expect from a high-end product. The narrow range of gear ratios is tailored to the masses, but does not do justice to the growing diversity in the gravel world. In particular, the lack of an option to ride with just one chainring is likely to annoy many prospective customers.
Shimano GRX Di2 - Background
For component leader Shimano, the GRX introduced in 2019 was a no-brainer. After all, you couldn't go far wrong with the first designated gravel bike groupset at the time if you wanted to equip one of the new off-road racers. Customers and manufacturers almost blindly trusted that the company with decades of expertise in mountain bike and road bike drivetrains would combine the best of both worlds and deliver the usual Shimano quality. Accordingly, the groupset was often bolted onto production bikes in various quality levels. Whether as an entry-level version with only ten mechanically actuated gears or with top-class flair as a 2x11 electric drivetrain: with the gravel bike boom, the matching Shimano components also sold like hotcakes.
Most buyers were also satisfied with the groupset. Of course, the GRX - like all Shimano groupsets - worked great mechanically. However, discerning Gravellers who were looking for something more exclusive than just a sporty commuter and leisure bike may have been disappointed by the Shimano range, as it was mainly focussed on affordable and mid-range price categories. In terms of drivetrains, the Japanese fell behind immediately after the presentation. SRAM used twelve instead of eleven sprockets for its AXS, which was presented at almost the same time; the "XPLR" offshoots of the road bike groupsets offer attractive options with a single chainring and cassettes with sprocket sizes up to mountain bike dimensions.
Competition from SRAM and Campagnolo
The drivetrains without front derailleurs became popular thanks to SRAM, especially on gravel bikes - the Americans achieved a considerable market presence on high-priced bikes, which should actually bother Shimano. Campagnolo went one better and introduced the Ekar in 2020, which does not shift electronically, but with 13 sprockets is the most complete single-speed transmission for off-road use to date. Shimano couldn't keep up: As a 1x11 groupset, the GRX was a rather poor compromise; as an inexpensive 1x10, it was almost unusable off-road because the gear range was too narrow. With Campagnolo and SRAM, you can also build significantly lighter (albeit more expensive) bikes. An otherwise identical GRX bike was inevitably up to 300 grams heavier because the Japanese opted for a more robust design and a lot of aluminium instead of carbon. A competitive high-end product for high-quality gravel bikes was therefore completely missing from the Japanese portfolio.
Shimano GRX Di2 - high expectations
It was not to be expected that a new edition of the GRX would turn the structure completely upside down. The Japanese company's policy is traditionally too conservative for that. Nevertheless, the expectations for a new GRX Di2 were high - also because the update of the mechanical GRX last summer was extremely economical and not very innovative. At the same time as the mechanical 105 road groupset, it was given a twelfth sprocket, a new rear derailleur and slightly modified shifters, but otherwise remained largely unchanged. As a 1x12 drivetrain, it can theoretically be configured with components from the mountain bike range, but there are only two sprocket options in the matching XT groupset (10 -45 and 10 -51), which require a Microspline freehub due to the smaller initial sprocket, which is only available for a few road or gravel bike wheels. This makes things quite complicated.
How does the Shimano GRX Di2 perform in the test?
Even the first glance at the market leader's new gravel flagship shows that the update to the electronic groupset is limited to a careful facelift. It adopts the brakes and drivetrain from the mechanical version, with only the shift brake levers, front derailleur and rear derailleur being genuinely new. However, the further development of these components is also limited, but more on that later.
In practice, however, you can hardly complain about the function of the groupset. As with the current road bike groupsets, the grips are now wirelessly connected to the shifting components and Shimano promises a service life of up to four years for the button cells. The shape and mounting have been slightly adapted to the flared handlebar ends of typical gravel bike handlebars, so that the transition to the handlebars is more ergonomic and the brake levers protrude less to the side. Otherwise, little has changed at the contact points.
Large and non-slip hand rest
The pleasant design of the shifter grips is still unrivalled, especially when the hands are resting on the grip bodies. The hand rest is large and non-slip; the small, steeply protruding front grip hump provides a good grip. At the same time, the grips are very slim, so that even small hands can get a good grip when things get rough. The brake levers also provide a wide contact surface for the fingers. The high pivot point of the brake lever and the "Servo Wave" braking force support mean that there is no need to switch to the lower handlebars even on steep descents; there is sufficient braking force available even in extreme situations. A freely assignable additional button, which was previously hidden under the rubber grip on the top of the hump, has been moved to the inside of the lever within thumb reach. It is too stiff to be assigned a shift function, but it is well suited to operating the computer.
Super switching behaviour
As expected, the shifting behaviour at the front and rear is excellent, but the front derailleur is quite loud. The howling motor noise is reminiscent of the first Di2 generations, whereas the current road bike front derailleurs work much more discreetly - and are also visually less noticeable. On the rear wheel, the new rear derailleur works quickly and precisely. The tried-and-tested damper reliably prevents the chain from slapping in the event of vibrations. The gear ratio with two chainrings at the front and 11-36 cassette - manufactured to 105 level - should be a good fit for most applications. Gear reductions for the mountains are on board as well as fast gears, and as a twelve-speed package, the gearing is pleasantly finely graduated. However, if you have individual requirements for your gravel bike gearbox, the GRX Di2 is not for you.
No operation with single crank
Unlike its mechanical counterpart, the rear derailleur is not designed to handle sprockets with more than 36 teeth. There is also no alternative to the double crankset with 48/31 teeth. Operation with a single crank without a front derailleur is therefore ruled out. If you want, you can still ride the somewhat sportier 11-34 gradation from the road bike groupsets, but there are no other alternatives. Adventurers with luggage who need extremely light gears on steep climbs are not what Shimano has in mind with the GRX Di2.
Conclusion on the Shimano GRX Di2
This and the lack of a simple option could cost Shimano customers, as the simple operation of these drivetrains is now a selling point for many riders. This also limits the possibility of wide tyres: With a maximum of 47 millimetres, the majority of gravel bikers should be able to gravel well; however, those who want to ride rough terrain and wider tyres will inevitably migrate to the competition. Nevertheless, one thing is certain: the GRX Di2 will also find many buyers. Above all, attractive complete bike offers will contribute to its popularity, which, depending on the brand, will be around 5000 euros and thus comparable to bikes with SRAM Force. These will only be chosen by those who don't want a front derailleur.
Suitable wheels and pedals
To round off the groupset, Shimano has added matching wheels and SPD pedals to its programme with the twelve-speed generation of the GRX. The RX880 wheelset comes with 32 millimetre flat carbon rims with an inner width of 25 millimetres; Shimano recommends tyres between 32 and 50 millimetres wide. According to the manufacturer, the weight is just under 1400 grams. A special feature is the quick-release freehub body; there is the classic HG standard as well as a Microspline freehub, which allows the installation of XT mountain bike cassettes. The retail price is 1649 euros. The corresponding GRX-SPD pedal is not a novelty, but the mountain bike pedal from Shimano's XT groupset in a matching design. The pair weighs 342 grams at a price of 135 euros.
Jens Klötzer
Editor
