Shimano GRX RX825 Di2 Gravel Groupset First Ride(s) Review

Chipps reports on his first impressions after riding 100 miles on Shimano’s new flagship electric gravel groupset – GRX RX825 Di2

• Brand: Shimano
• Product: GRX RX825 Di2 Electronic Gravel Groupset
• From: Freewheel
• Price: STi Di2 levers including brake calipers: £399 (right) £399 (left). Chainset £229. Rear mech £349. 11-34T Ultegra cassette £119.99. 11-36T CS-HG710 cassette £84.99. Rotors £54.99. Chain £49.99
• Tested by: Chipps for 150kms

Before we get to the ‘Aren’t I lucky?’ bit, here’s a quick summary.

Pros

• The lever and hood shape. Even better than GRX RX-820 mechanical. Excellent comfort and controls in the hoods.
• Easier to reach, more outboard STi buttons. Extra third buttons for whatever you want.
• Ability to run Synchro-shift so that you only ever need one shifter
• Braking power is excellent (as far as I can tell with the ‘wrong’ hands…)

Cons

• Would like more reach adjust on the brake lever for smaller hands
• Despite the 48-31T chainset and 11-36T cassette option, I’d still like a lower bottom gear for the riding I do.
• There’s no 1×12 GRX Di2 setup – yet. (See my Conspiracy Theory below)

Earlier this month, I was lucky enough to get an extended few rides on the much-anticipated Shimano GRX Di2 groupset in some pretty special circumstances. Thanks to a multiple alignment of the stars, Stage 9 of the 2024 Tour de France included a significant proportion of ‘chemin blanc’, ‘strada bianchi’ or if you’re not a cycling tifosi, just ‘gravel’. And that’s where I got to ride it.

Riding at the Tour

This early-July date coincided with early production samples being available of Shimano’s newest gravel groupset and, while none of the Tour pro teams were running any GRX (hey, even pro cyclocross racers only use Dura-Ace) on that one stage, it was an ideal opportunity for Shimano to showcase the groupset to a select few bike journalists.
In addition, the Tour Stage 9 date fell a day after the Eurobike show finished for the press, making it work time-wise. And finally, the Tour stage in Troyes was (if you squinted) right on my way home from Eurobike. It seemed that all of the stars had indeed aligned.

Shimano is placing a lot of its might behind its GRX groupsets. It has seen demand for road bikes ‘soften’ a little in the last few years, along with the ‘everyone who wanted one, now has one’ world of mountain bikes (and the absence of any groundbreaking new XTR/XT groupsets yet…) and things are looking a little quieter in the extremes of pure road and pure mountain biking. Gravel, in all its forms, meanwhile is booming.

However, a new, sorted, tubeless, gravel bike is arguably the road bike that 50% of road riders actually need for the pothole-resistance, gear range and ‘what’s down there?’ versatility. A gravel bike is also the bike that can appeal to the ‘ridden for years’ mountain biker who is either bored of how capable their modern MTB is, and is looking for a new challenge, or it’s the kind of ‘all terrain’ bike that’ll appeal to anyone who doesn’t live at the bottom of a mountain (or massive hill at least…)

Hence, Shimano’s big efforts to show the world its new GRX groupset. And, although the lion’s share of OEM spec is with 2×12 mechanical groups, Shimano is predicting a sizeable takeup of this, its new, semi-wireless GRX RX825 Di2 system.

GRX Di2 Recap

Just in case you missed out, a quick summary: GRX Di2 is 2×12 only. The existing mechanical components, of 11-36T and 11-34T cassettes and 48/31T chainset, carry through. The cassettes spin on regular Hyperglide freehubs.

The difference, naturally, is in the new Di2 brake/shift levers, the electric Di2 front and rear (clutch) mech and that it’s battery powered and semi-wireless. Semi? The shifters are wireless and they communicate wirelessly with the rear mech, which is wired to the front mech and an internal battery. Shimano reckons this allows a greater battery range: depending on shifts, you should get months of life out of the rechargeable, internal battery (and nothing to do with SRAM apparently having a patent on removeable mech batteries… ahem)

You might have seen my previous review of GRX mechanical, but with the new RX825 tier, the riding experience is very different with Di2, so read on for my impressions after three reasonably long rides on the new setup. What I haven’t mentioned is that, thanks to Shimano’s sponsorship of the Tour de France (it provides the iconic blue neutral support cars) we got some mind-blowing access to the actual course that the Tour racers would be competing on, just for a bit of real-life realism. Over 60km of it, including the final eight gravel sectors and the finish in Troyes itself… on the afternoon of the race itself, just a couple of hours before the pros came through. It’s one thing trying to ride fast on a random press launch fire road, but it’s another thing riding flat out in a bunch, trying to stay upright on flat gravel corners while barbecuing spectators cheer on this load of scruffy, random riders who appear to have a support car and photo moto…

In addition to the 60km of Tour de France madness, we also got two more 40km rides around the white roads of the Champagne region. One was a very ‘what’s down there?’ UK style of ride, which saw us plough through muddy wooded tracks and field edges, while the other was more road based with some chunky gravel thrown in. I reckoned that was enough to bring you some first impressions.

Shimano GRX Di2 First Rides Impressions

New STi unit Brake Hoods and Levers

Let’s start at the front. There’s been a lot of work that has gone into the hoods and levers on new GRX Di2. After all, this is probably where you’re going to be spending 90% of your time, so it makes sense. Compared to my 12 speed Ultegra Di2 road bike, and even GRX Mechanical, the GRX Di2 hood tops are very different. They have a very flat profile that works as an extension of the bar’s forward sweep, giving you a load of handlebar real estate to move around on. At the lever end of the rubber, there’s a sharp, pronounced rise up to the lever pivot and mechanism to anchor your hands. This is way more comfortable than I’ve made it sound… In fact, I think I only left the hoods once during the Tour stage, they were that comfortable.

Adding to that comfort are the brake levers themselves. The levers are very flat-fronted (like old GRX Di2 and very unlike the rounded blades of my Ultegra). This allows an ‘always covering’ finger position over the flat blade, which feels very natural.

GRX Di2 has raised the pivot point for the brake lever. This allows a lot more power at the lever, due to an increased lever ratio. The higher pivot has also freed up space behind the lever for your ‘spare’ fingers to sit. However, I did find the reach felt very far-out for my average length fingers. I had the levers dialled in as far as they’d go and would still have liked them closer – perhaps this a mountain biker thing that I like my brake levers almost touching the bars, whereas road levers aren’t used as much or for as long? At least it was a quick job with a long 2mm Allen key…

Adding to my brake worries was the fact that swapping over from ‘Euro-style’ isn’t an easy or quick job on a drop bar bike, so I had to run my loaner Canyon Grail euro-style and resort to labels and not being too heavy-handed on the levers. I’d like to spend time on some UK-spec brakes to be sure as they feel super powerful, but my brake stabs lacked the same finesse as car braking with the wrong foot…

We’re still talking about the levers, as there’s still much to mention. The lever blades are coated with a subtle, grippy surface, borrowed from Shimano’s fishing department, ideal for bare hand brakers and riders in the wet. Nestled behind the lever blades, and equally reachable in the drops or the hoods, are the two shift levers. These have been moved outboard by 2.5mm so that they sit prouder of the brake lever blade. This is great for being able to find the correct shift button when being bounced along, especially with full finger gloves, though Shimano missed a trick by not making the shift ‘click’ more positive than the mouse click feel it shares with the road groups, so it can still be hard to feel that you’ve actually clicked the shifter.

Front Shift Next
I said the ‘two shift levers’ – there’s actually a third shift button on both shifters. This is an easily thumbable button under the hood rubber, just on the inside edge of the hood ‘upright’. This button can be programmed with Shimano’s E-Tube app to basically do what you want, including what Shimano calls ‘Front Shift Next’ where pressing a button will cause the front mech to shift to wherever it isn’t currently. So if you’re in the inner ring, it’ll shift to the big when pressed and vice versa.

You can re-map any of the buttons to do this, though the suggestion is that you could use Shimano’s Synchronised shifting to shift sequentially through both chainrings’ worth of gears using just the right hand shifter. The left hand shifter main buttons could then do the same, or operate Front Shift Next and a shift up function, while the thumb buttons could change screens on your Garmin. It’s all in there apparently (and it’s a firmware update on current Ultegra and Dura Ace)

Shifting itself felt very fast across the block, with changing while sprinting a simple thing, and panic shifts across the 11-34 (or 36T) block no problem. Shimano road front shifts have been as crisp as a rear shift for years and new GRX doesn’t disappoint here either.

In my review of mechanical GRX RX820, I said that I have used a mostly-GRX Di2 setup on my cyclocross bike for many years, many races and many Three Peaks, so I had high hopes for this new group. Am I going to upgrade? We’ll see, as I still want to see what the eventual one-by GRX groupset is like.

Conspiracy theory

To be honest, I can’t see Shimano launching an electric 1×12 shifter and mech capable of shifting over a mountain bike cassette until it has come out with exactly that thing for mountain bikes first (presumably on the ‘Must be out one day soon?’ next XTR release – though it didn’t make the Olympics… At least with 2x GRX Di2, it is fully ‘normal’ Hyperglide compatible, so an upgrade for existing 2×11 users isn’t going to need sourcing Microspline wheels, though you’ll still need a 12 speed cassette.

Shimano GRX Di2 Conclusion

Is the new GRX 825 hood shape good enough alone to win me over? I think it is. It’s such a naturally comfortable place to spend time, with the shifters easy to hand, extra gadget buttons (and the option of satellite shifters too if you want to put them on the ends of your aero bars. Wierdo.) that I’m very tempted. And, contrary to what I probably said in May’s GRX mechanical review, you CAN plumb in Shimano’s neat in-line ‘chicken levers’ for handlebar-top braking if you want. Although even Shimano’s European staff seemed puzzled why anyone would need them. (Anyone without a dropper on their gravel bike would probably be equally confused, I reckon).

Talking of puzzled Shimano Europe (based in Holland) employees, I still reckon that having an extra 12th gear, but no greater gear range is missing a trick. It’s only those riders used to long, flat road rides who are that bothered about perfect cadence. The rest of us would rather have a lower bail out gear for a loose or long gravel climb than smaller hops between ratios.

Even compared to current RX820 mechanical GRX, the Di2 hood shape is a massive step up. Add to that the power of the brakes and the general ergonomic improvements and I reckon I’m sold. Shifting is intuitive and fast. Braking (with the wrong hands) is powerful too. The two-button shifter is still not as ‘panic shifting blind’ easy as SRAM’s single shifter a side system, and never will be, but it’s still simple to get used to and easy to use.

With a less fanboy head on, I’d like to see clickier buttons, more lever reach adjust and, hmm, that’s about it. Obviously, if you’re looking to upgrade a bike that has no internal battery room (it’s not routed for it, the tubes are too small, or perhaps you’re running a dropper post) there’s no provision to run an external battery, as on earlier Di2 incarnations. There’s still the possibility of the shifter wires coming unplugged in a crash or clumsy moment (as actually happened on our pre-Tour shakedown ride) but they can be replugged with someone with strong fingers. A cut wire, not so much.

In terms of weather-resistance, I have no worries at all for extended winter use. I’ve literally submerged previous versions of GRX without incident (and then put the bike away wet in favour of going for a curry instead of standing in the yard, washing it on a December evening… it still shifted first time, a week later.) There’s no longer even a control box to soak, as all of the brains are in the rear mech and the battery is hidden safely inside the bike frame.

What’s the cost, Mr Wolf?

The STi shift/brake levers will set you back £399, per side, with bled calipers. Add on £184.99 for the front mech and £324.99 for the rear and that’s already a big investment. And that’s even before cranks, rotors, mounts, battery and a chain. You won’t get much change from a couple of grand. And then you’d have to assemble it. However, Shimano doesn’t have the likes of us ‘frame plus aftermarket groupset’ serial upgraders in mind and you’re far likely to see a perfectly assembled complete bike winking at you from the computer screen or through the shop window. I think in those forms, with complete bikes around five grand, complete with fancy wheels, the whole GRX825 Di2 system is going to make far more sense. Not least because you won’t have to thread the shifter wire down the chainstay…

I see that the likes of Canyon already have the Grail CF SLX for sale in the UK, so you’re going to start seeing these out and about very soon. We’ll see how well it goes down in peak gravel adventure season.

And finally some self-indulgent photos from a big day out on the gravel roads of France, being chased by the real peloton.

Thanks again to Jonathan, Erik, Chelsea, the rest of the Shimano and the ASO crews who sorted out an incredible experience.

All the great photos here are by: Yorit Kluitman

Oh, and thanks to a glitch, I appear to be unable to answer comments on stories at the moment. Let’s take it to the forum if you have questions – just @chipps me…