Shimano GRX RX820 Mechanical Gravel Groupset review

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 …

By chipps

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Review: Shimano GRX RX820 Mechanical Gravel Groupset

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…

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.

https://productinfo.shimano.com/en/compatibility/C-454

 

 

 

Fair point!

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?)

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

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

 

 

Another product where Shimano “just works well’…

How does it compare to Sword?

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.

 

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.

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.

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.

 

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?

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

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

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.

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.

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

 

@swanny853 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!

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)

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

 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 😎

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!).

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