Shimano GRX RX820 Mechanical Gravel Groupset review

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Chipps, perhaps perversely, specified his test on Shimano GRX RX820 to cope with gravel riding that was more mountainous than groomed, how did he get on?

  • Brand: Shimano
  • Product: GRX RX820 Mechanical Gravel Groupset
  • FromFreewheel
  • Price: STi levers including brake calipers: £349 (right) £329 (left). Chainset £229. Rear mech £119. 10-51T cassette £159.99. Rotors £54.99. Chain £49.99
  • Tested by: Chipps for 6 months


  • The lever and hood shape. A very comfy place to spend a long time.
  • That 40 x 51T complete bailout gear.
  • Honourable mention to the Genesis Croix de Fer Titanium frame. That frame with DT Swiss wheels and GRX groupset makes an amazingly versatile rig.


  • A greater reach adjustment on the brake levers
  • Chainrings in more than just two sizes (40 or 42T)
  • UDH compatibility. Hey, it’s a wish list, OK?

When ‘new’ GRX RX820 was launched at the end of last summer, I was very interested to get to try it. For years, my cyclocross bike had been running a mishmash of Shimano GRX and Ultegra, to give a wide ranging 2×11 setup, with GRX Di2 shifters (and its great brakes), a GRX RX600 46-30T chainset and an Ultegra Di2 mech, just ‘cos that’s what I had. However, I’ve spent a load of time on SRAM XPLR 1×12 groupset and was keen to see how they compared.

I was keen to try to GRX 820 in its one-by incarnation because it would let me run a mountain bike-like 10-51T XT cassette and a single ring. Yes, I realise that not everyone wants a massive one-by range on their gravel bike, but I do. I’ve banged on before about how I think that there are two, distinct camps of gravel riding: There’s ‘American’ or ‘London’ gravel, where a rider clips in, rides flat out for four hours of mildly rolling, fine cinder towpaths and farm tracks, has a cappuccino and avocado toast and then rides a couple more hours home. This style of riding is where aero wheels, Lycra shorts with pockets and file treads make loads of sense.

Then there’s ‘Northern (UK/Canada/Europe) gravel’ where it’s more akin to 1990s mountain biking. Trails tend to be narrower, more natural and less predictable, with more emphasis on bike handling skills (and fun). There’s a lot more ‘Ooh, what’s down there?’ on/off road riding and climbs tend to be unrelenting and steep. The same goes for descents. This is where we see gravel bikes with chunkier tyres, perhaps a small travel suspension fork or dropper post and where the need for gear range over smooth cadence dominated. This is where I do all of my gravel riding. I have a SRAM-equipped Rä gravel bike with SRAM’s XPLR groupset (and its 1×12 10-44T x 38T chainring gear range) that regularly sees me grovelling in bottom gear for an hour.

Shimano’s UK distributor, Madison, was kind enough to install the group onto its flagship Genesis Croix de Fer Titanium frameset, complete with a nice set of DT Swiss Microspline wheels. At launch time, the only Shimano Microspline option was the £1200 carbon rimmed GRX wheels, but these DT Swiss hoops have been marvellous.

Starting at the front of the bike, let’s check out how the flagship gravel groupset lines up:

RX RX820 STI brake/shift levers

Shimano’s road STi levers have been around since the late nineties, and have evolved nicely with the times (with hidden cables and the addition of hydraulic brakes) to what we have here.

GRX brake/shift levers use the intuitive ‘pull for brakes, swipe the lever sideways for shifting’ action that is very easy to get used to. GRX differs from an equivalent Ultegra lever with a differently shaped lever blade – a matt-textured, anti-slip blade that’s flattened at the front for ‘finger on the lever’ comfort instead of the rounded and polished, more aero Ultegra lever. Shimano gets points for making the reach-adjust 2mm Allen key relatively easy to get to without disassembly of the hoods (though I would still like more ‘in’ adjustment for those with small hands, or ergo bars that put your fingers further from the levers). The hoods, too, deserve mention, as they’re far more aggressively textured for muddy hands to grip on to than road hoods. At the same time, though, the hoods are relatively round in shape, so that if you’re on a bike with flared bars, you’re not forced to rest your palm on a ‘corner’ of the hood, as you would if the hoods were squarer in shape for on-the-tops comfort on road bars.

Grippy, but well-rounded

Shifting action was reassuringly mechanical-feeling, without any plastic ‘clacking’ and the levers shifted smoothly through the dozen gears available. Shimano’s road brakes are generally excellent and here we get the finned brake pads and Freeza discs more familiar to mountain bikers, although GRX calipers are flat-mount only (and always have been). If you’re looking to modernise an older gravel/adventure bike, GRX doesn’t officially make post-mount or IS-compatible calipers (though some unofficial workarounds are available…)

Gears: 1×12 10-51T

Going back to the gears, when GRX RX820 was announced, there were three options – a 2×11 groupset as we’ve already mentioned, and then two 1×12 setups. I chose the 1×12 10-51T setup because I wanted a wide range of gears and didn’t mind having bigger jumps between ratios.

Over six months of weekly use, the Croix de Fer has been used on everything from almost-mountain-biking on very chunky trails to smoother gravel tracks. I even banged out a 100km road ride to see how the gearing and comfort of the system fared under longer rides. The system performed very well in all of those situations, with the wide range of gears coming into their own on extremes of terrain – with the super steep climbs and equally steep descents of my local terrain serving as a great test. If you live, ride or plan to ride somewhere flatter or more rolling, you may benefit more from the 2×12 setup, but for what I ride, the 1×12 has been great.

GRX Brakes

The Croix de Fer came with ‘stock for gravel’ 160/160 rotors, which proved fine for both choppy, technical moves and long, draggy descents too. The Freeza rotors and finned brake pads both offer a claimed temperature reduction of 50°C each and I certainly noticed no pump or fade, even on 15km downhills [Ed – #humblebrag]. Despite Shimano’s Servo Wave technology included in GRX levers, I feel the previous generation had a little more ‘snap’ in whizzing the pads into contact with the rotor, but both GRX incarnations give great power and modulation. As mentioned, the flat-mount only is going to limit riders with older frames, but any gravel/cross and even some hardtail frames from the last half dozen years should be a direct fit.

Final thoughts: GRX RX820

I did kind of expect a ‘choir of angels’ moment with the GRX group, given that the original Shimano GRX was pretty genre-defining when it was launched in 2019. Perhaps it shows that Shimano got it pretty much right the first time, five years ago, (a little like it did with the SPD pedal). Modern GRX 820 by comparison only really adds an extra gear… The braking is still great and the shifting is crisp, even across some pretty extreme chain angles. Would I prefer a 2×12 system for the riding I do? Not really – even though it’s obviously where Shimano is putting most of its focus. 2×12 is well-suited to ‘commercial’ gravel racing, where events are more like dirty road races. However, I feel that the 1×12 system, with its simpler cabling needs and lack of chain jamming and dropping (and perfectly adequate spread of gears for most people), is probably of more interest to riders coming from mountain biking rather than from the road.

I’d moan about a lack of Di2, but then it’s obvious from looking at the road (and previous GRX) developments that electric shifting is going to be arriving very soon for GRX. And, I am aware that Di2 off road is usually the preserve of pro racers and pampered journalists. Adventure riders are far more likely to want something that doesn’t need recharging.


After six months of use, Shimano’s new GRX RX820 is a great groupset for gravel riders who need a good spread of gears, faultless braking and reliability. It was only the success and ‘right first time’-ness of ‘old’ GRX that makes it feel slightly disappointing. And that’s purely because GRX RX820 simply gets on the job at hand without any fuss.

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Viewing 22 posts - 1 through 22 (of 22 total)
  • Shimano GRX RX820 Mechanical Gravel Groupset review
  • 13thfloormonk
    Full Member

    Curious rational for going 1x, I mean, you could easily achieve lower (and higher) gear with a 2x setup and still run a less gratuitous cassette (46/30 + 11/42?) which in turn would reduce the extreme chain angles (or at least extreme derailleur stretch) and in my experience gives a smoother running drivetrain. Plus the only chain drop I’ve every experienced has been on my 1x bike 😂

    It’s my 2x bike I use for summer exploring and has taken me around the outer Cairngorm loop amongst other ‘definitely MTB in places’ adventures.

    But I do get it, I use the 1x bike (my old CX bike) as a sort of winter-smashy bike, dragging it through the sort of mud and winter trail debris I wouldn’t like to expose my 2x drivetrain to, if only for less cleaning. Those aren’t the sorts of rides where I go deliberately looking for long climbs though…

    Full Member

    The largest officially compatible sprocket in a 2x is a 36T and with RX820 it looks like you get a 48-31 combination, not 46-30 (that’s RX610) so I guess Madison aren’t going to hand out unsupported combinations.




    Full Member

    Fair point!

    Full Member

    I came here to say that 🙂 But also with my other point about testing the 1x setup rather than the 2x… I’m not anti front-mech at all, my road bike has newer Ultegra 2×12 and my ‘cross racing bike is mostly GRX Di2 2×11…
    However, I’m aware that the nearest competitor to the new GRX groupset is SRAM’s 1×12 XPLR/Apex Mechanical groupset, which has never had a front mech, so I wanted to see how it did against it. The biggest drawback to it (IMHO) is that there is only one official XPLR cassette and that is the 12 speed 10-44T one. To get a bigger range, you need a mountain bike mech and cassette – which in the digital SRAM world is less of an issue (although, how much?)

    Full Member

    I used an XT cage to convert my RX600 derail to accommodate at 50T cog.

    Full Member

    It’s the parallelogram shape that differs for wide spread cassettes – the long cage increases total capacity rather than cassette capacity.



    Full Member

    Another product where Shimano “just works well’…

    How does it compare to Sword?

    Full Member

    I have two gravel bikes,  a ti camino 11 speed grx with 46/30 front and 11-40 on the back.   This bike has been for 100 mile US type gravel rides,   Blue and Red MTB trails in France which is more like UK gravel riding and huge road rides in the Pyrenees including the circuit of  death from Lauruns to Luchon.     Its covered everything admirably.  I’m put of the 12 speed as far as i can see a 11-40 or 10-40 12 speed doesn’t exist.

    I also have a flat barred Dolan with with a 36 at the front and 10-50 out back 12 speed.  The 36 was chosen when as i wasn’t as fit and coming back from injury,  this isn’t as versatile as the 2x,   I’ll probably increase it to 40 or 42 soon.  I’ll see how this set up goes before i’d consider switching 12 speed 1x.


    Full Member

    42×10-51 gives near as damn it same top end as 46×11-36 and slightly lower than the bottom gear. One gap in the cassette I find a bit big occasionally, but no other downside, and frees up LH for a dropper STI.

    Wouldn’t want lower gears than either of these offer by bodging a double with a wider than spec cassette as traction is insufficient on gravel tyres on looser surfaces to be beneficial – I already climb in taller ratios than I’d like from time to time to maintain traction.

    Free Member

    you could easily achieve lower (and higher) gear with a 2x setup and still run a less gratuitous cassette (46/30 + 11/42?) which in turn would reduce the extreme chain angles (or at least extreme derailleur stretch) and in my experience gives a smoother running drivetrain.

    But the gains you’re talking about are so minor, compared to the wonderful simplicity of a 1x drivetrain – including the benefits of a narrow-wide ring.

    I’d guess you fall into the first group identified in the article? Which is totally fine obvs.

    Full Member

    Curious rational for going 1x

    Was it? Seemed perfectly reasonable to me, lots of people are still going to want a premium 1x setup general purpose Gravel bike for “riding not racing”. That seems like a sensible basis for choosing to test the 1x version. 12 sequential clicks should be plenty to cover *most* people’s expectations of a Gravel bike now, for those in search of a more racey/road-bike-like setup 2x still exists but isn’t going to be the product pushed towards most muggles. Chipps chose to test what lots of people will probably end up buying.

    TBH What I’m more interested in is what is going to appear at the less premium end of the market for both 2x and 1x: RX400/RX600/Tiagra in 2×10/2×11/2×11/1×11 flavours all still exist, but those ‘mid-tier’ groups will be retired or replaced soon I assume.

    At the “bottom end” The promised CUES drop bar levers are still not on the market (that I’ve spotted) so I reckon plenty of people with Gravel racing/mixed on & off-road aspirations will want an affordable closer spaced 2x setup (with hydraulic disc brakes) that is going to be met more by those mid-tier GRX/Road groups than the RX820 group.

    SRAM seem far more committed to 1x for drop bars generally, the issue comes in the lower to mid-tier where customers potentially have more varied requirements I reckon.


    Free Member

    Your pros/cons list don’t seem correct? Seems more of a wish list for the pros, and then all the cons are actually pros?

    Full Member

    Running 11-51 on std 812 GRX with out mods apart from extra chain links on 2 bikes. Not sure why Shimano restrict the cassette size. Has this set up over 4 years and not noticed significant wear and it shifts as crisply as it always has

    Full Member

    @tmays – you are completely correct. I think there was some post-editing that went on that mixed the order up. Hopefully fixed now!

    Full Member

    Shame Shimano haven’t reduced the chainline for 1x, its the same as  GRX 810 1x and is pretty awful in the 2 biggest cogs on the cassette (significant bend in the chain and it runs noisy and draggy). It seems like GRX 1x is designed to work best with a 148 mm rear hub. I ran GRX 810 1x with a 142 mm rear hub, 40t GRX chainring and 10-42 Sram cassette and ended up changing the chainring to a Garbaruk 5 mm offset 40t. This has reduced the chainline and resulted in less chain bend, drag and noise in the 2 biggest cogs on the cassette.

    Full Member

    It’s the parallelogram shape that differs for wide spread cassettes – the long cage increases total capacity rather than cassette capacity.

    Top jockey wheel offset, defined by the cage, also affects available size of cassette. That’s how sram mechs have a horizontal parallelogram and still track big cassettes. Also how you could fit something like a oneup rad cage to a 10s shimano mech and clear a bigger cassete without a silly b gap.

    Full Member

    @thelooseone – agreed – I space my ring in 2mm


    True, but SRAMs parallelogram profile also changes between close and wide ratio. The bigger the cage offset, the bigger the reliance on accurate chain length which makes things awkward on FS bikes with chain growth – not generally speaking an issue on gravel bikes admittedly!

    Full Member

    I expect you can hook up the GRX levers to any old shimano 2 pot post-mount caliper – on my gravel frame I have tiagra flat-mount calipers with MTB flat bar levers and they work well (same brake fluid, same hose connections, pretty much same piston diameter I guess)

    Full Member

    Yes – did that with 810 11 speed STIs on old XTR calipers on another bike.

    Full Member

     the wonderful simplicity of a 1x drivetrain – including the benefits of a narrow-wide ring.

    I’d guess you fall into the first group identified in the article? Which is totally fine obvs.

    That’s why I was interested in the general tone of the review. I probably ‘identify’ more as a roady graveller, but ultimately I still end up in some reasonably spicy terrain at times, which is when I prefer the 2x bike which has a broader range and more gears than the 1x bike which I just use for smashing around short/relatively flat local loops.

    I guess a childhood of my dad shouting at me every time I got cross-chained means I’m not afraid of the front shifter, ‘wonderful simplicity’ of 1x is a very minor consideration compared to the range of a 2x system.

    Oh, and of course the aesthetics of having chainrings bigger than your sprockets, which is probably a roadie affectation 😎

    Full Member

    10-51 gives a similar but slightly wider gear range with a 42T ring compared to 46/30×11-36, so 1x no longer gives up range necessarily. Bigger ratio gaps obviously, but they mostly don’t bother me. 10-45 is a sensible option for closer gaps, but with a slightly reduced range – still way bigger than with 11-42 though. Would like to try it with a 40T, so that low end is close to the low gear on 42×10-51. Dropping the biggest gear down a little might be worth it. Dunno. Don’t miss being in the trim zones a lot of the time for stuff I tend to ride when I had double (which I thought I loved!).

    Full Member

    @alanclarke – this link shows what calipers are compatible with GRX levers.

Viewing 22 posts - 1 through 22 (of 22 total)

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