Shimano is the first drivetrain manufacturer to bring a dedicated gravel/adventure groupset to market.
Announced earlier this year, GRX is available at Tiagra (RX400, 105 (RX600), and Ultegra (RX800) levels, with the last of those including Di2 options.
Shimano says it’s been working with others to ensure that the drivetrain delivers for gravel riders, including Garmin (for navigation that integrates with Di2 levers), and the Shimano Gravel Alliance — a group of 16 riders that reported back on products and put forward ideas.
I had the chance to ride the top-spec Ultegra Di2 version at Shimano’s press camp in Montana and I came away impressed.
My GT Grade Carbon test bike was built up with GRX Di2 and GRX 650b wheels. Kevin Fickling / Shimano
I have to admit to initially being a little sceptical about GRX, as it seemed less like a new groupset launch and more like a collection of parts from existing mountain bike and road products. Having tried the components, I can report that that’s simply not the case.
As part of the launch and test process, Shimano asked me to supply a frame onto which it built the new GRX Di2 group. I opted for GT’s new Grade, a bike I really enjoyed riding on its launch this year and that I’ve spent plenty of time riding back in the UK, appreciating its combination of a light frame (sub-1kg) and rear-end compliance.
As soon as I started running through the options list, a few choices needed to be made, though. I opted for 1× — up until then I’d only ridden a 2× Grade — and I also chose 650b wheels because I’ve not tried them out on the Grade yet. Gearing-wise, I went with the wider 11–42t cassette option, plus with a 40t front ring to give a decent low climbing gear for when things got tough and steep.
Other options, such as the satellite shifters mounted on the top of the bars, mimic one of my favourite setups from SRAM’s Red eTap group — I like to have the blips mounted on the tops for shifting when I’m grinding my way up a climb. Finally, I chose the intriguing sub-brake levers (BL-RX812) which run inline from the Di2 shifters and offer braking from the tops, just like cross-top levers of old.
This choice did mean that I couldn’t fit a standard Garmin out-front mount on the PRO Discover bar setup I’m running, and I’m now on the lookout for an alternative, such as this F3 FormMount.
The lined textured section on the inside of the hoods is a hidden button, I assigned mine to switch between screens on a Garmin Edge 530. Warren Rossiter / Immediate Media
Shimano has worked with Garmin to allow you to control your Edge head unit via the GRX Di2 levers. Shimano had previously worked on its own head unit to rival the leading GPS units, an update to its old Flightdeck computers from the 2000s, but perhaps wisely took the decision to scrap that project and concentrate on what it does best, leaving computing to the experts.
Existing Di2 levers have a ‘hidden’ button on the top that, when combined with the added WU111 Bluetooth antenna, enables the Di2 to sync with a Garmin head unit, but this new RX815 shifter positions the integrated button on the inside of the hood.
These buttons can be assigned to operate switching screens on the Garmin head unit, so you don’t need to take your hands off the bars, which is even more important when riding on gravel.
On 2× systems you can use the Garmin head unit to activate Synchro Shift (which autoshifts the front derailleur, and/or compensates for the rear derailleur at the same time). You previously had to switch between these modes with a double click on the Di2 control box.
Your Garmin will also be able to display the Di2 system’s battery level — and give audible warnings when it’s low — and indicate which gear you’re in. You can assign the Di2 shifters’ auxiliary buttons to any ANT+ compatible device, such as Garmin’s own lights, or use them to switch through power modes on Shimano STEPS e-bike motors.
The full Di2 control and shift settings are standard on the latest Edge 530 and Edge 830 head units, but for the 1030 it’s currently a public beta-update. However, in the not too distant future, it’ll be standard on all Edge firmware. You can allocate Di2 button operations without a Garmin via your phone, by connecting to the system using the WU111 through Bluetooth and the E-tube app.
GRX Di2 is pretty much exactly what you’d expect. The smooth, accurate shifting of Di2 is matched to a single chainring setup in this case, and the rear mech’s clutch mechanism eliminates chain-slap.
Over a day’s riding at the Shimano press camp, the chain didn’t drop, slip or step out of line in any way. That’s pretty much what I’d expect from any Di2 setup; no surprises and not much of note to report there.
But the GRX RX815 STI units are a marvel. The hood shape, lever shape and lever actuation are all unique to the Di2 model with other models having a much more traditional lever design.
The hood is one of the most comfortable I’ve used on any groupset, but then I’ve never really had an issue with many, and having big hands I didn’t mind the old lumpy BR-405 lever.
GRX Di2 is the first drop-bar groupset to get Shimano’s Servo Wave tech, normally found on mountain bike components, and it is simply brilliant.
Servo Wave is more about brake action than anything else. The initial brake pad travel is fast, so little movement is required to get that initial contact; then the power ramps up rapidly through the lever stroke, making for some of the best from-the-hoods braking I’ve experienced.
As I’ve said, with bigger hands, I don’t have a problem braking from the hoods using standard levers, but it’s a known issue for smaller handed riders.
I was more than comfortable staying up on the hoods and single-finger braking on the trails on some fast, rocky and truly twisty mountain bike trails at Montana’s awesome Whitefish bike retreat trails. Usually I would have been down in the drops.
I’d also opted for a 160/160mm Ice Tech rotor setup and it’s the most impressive braking I’ve experienced from Shimano yet.
The sub-brake levers didn’t detract from the brake performance at all, and the lever action from these feels similar to the STIs’, though the smaller lever means they give a little less feel than a full-sized brake unit.
The 650b GRX gravel wheels are up to Shimano’s usual standards when it comes to quality, but only time will tell how these hold up.
650b with the bigger volume tyre choice it affords is brilliant when you’re riding on the truly rough stuff, but being the only rider in our group with larger volume tyres meant I was working harder on tarmacked road sections to stay at pace.
In an ideal world you’d have both wheel options, but that’s a lot of extra cash to spend, so my advice is to think about what you truly want from a bike of this type before committing to one wheel size or the other.
Overall, my first impressions of GRX Di2 are wholly positive. The accessory shifters and brake units mean that you can customise to your heart’s content, and the STI shifters are a masterpiece of ergonomics.
It got me thinking that, aside from dedicated amateur racers and pros, most riders spend the majority of their time on the hoods, and that’s where these new levers shine.
If I was putting together a Di2 bike of any drop-bar persuasion, I’m pretty sure I’d opt for the RX815 levers over the standard road alternatives.
A single 40t chainring and a 11-42t cassette gives a wide range. Kevin Fickling / Shimano
Shimano GRX Di2 test bike build specs
- Weight: 9.5kg (size L with Shimano XTR PD9100 pedals)
- Frame: GT Grade
- Fork: GT Grade carbon
- Chainset: Shimano GRX 810 Hollowtech II, 40t chainring
- Chain: Shimano 11-speed
- Brakes: Shimano GRX RX810
- Shifters: Shimano GRX RX815, satellite shifters, WU111 Bluetooth antenna
- Rear mech: Shimano GRX Shadow RD+
- Wheels: Shimano GRX 650b
- Tyres: Vittoria Terreno Dry 650b×47mm
- Bar: PRO Discover aluminium bar
- Stem: PRO Discover
- Saddle: PRO Stealth
- Seatpost: PRO Discover dropper
- Bottle cages: PRO carbon
Shimano GRX Di2 pricing
- Shimano GRX 810 Hollowtech II, 40t chainring: £200
- Shimano BL-RX812 sub brake levers: £60 (each)
- Shimano GRX Di2 RD-RX817 rear mech: £290
- Shimano GRX ST-RX815 dual control levers: £220
- Shimano GRX BR-RX810/ST-RX815 brakes and shifters: £310
- Shimano GRX 650b wheels WH-RX570: £90 (F) £210 (R)
|What we tested||FC-RX810-1 Hollowtech II 1× crank with 40t chainring, BL-RX812 sub brake levers, RD-RX817 rear derailleur, ST-RX815 levers, BR-RX810/ST-RX815 brakes and shifters, WH-RX570 wheels|
|Features||Optional satellite shifters, user-assignable auxiliary shift buttons, Garmin integration.|
|Brake type||Hydraulic disc|
|Cassette options||11-speed Shimano road and MTB cassettes (compatibility varies according to gearing)|
|Chainring options||1×: 40t, 42t. 2×:48/31t|