Shimano GRX 12-speed (2023 GRX820/610)

The long awaited GRX 12s seems to be all but confirmed, with companies starting to list 2023 version gravel bikes, with the new gear already!

From the leaks I have seen so far, we can gather:

  • new groups will be called 820 and 610
  • both are 12s, cross compatible and offer 1x and 2x options
  • 1x is mullet compatible with XTR (11-51)
  • 2x is keeping its‘ chainring sizes of 46/30 (610) and 48/31 (820)
  • the standard cassette is not micro-spline, with an 11-36 cassette (like on the 12s 105)

Here is what Luca Bikes has given us:

*The last Luca version was sold out in no time. But that doesn’t mean we’ve rested on our laurels. The 2023 model has been further developed. Luca comes with an even lighter Reynolds steel frame, more connection options and the high-quality Shimano GRX 1×12 groupset with an even larger shift range. This will make D.Y.B. one of the first manufacturers to install the new groupset

Pre-order your Luca now for next spring.

Until December 31, 2022 with a pre-order discount of CHF 500.-.*

And this is orbea:

Really looking forward to this, with 2x for gravel really being a little neglected in my mind!


Exciting! I guess all we still need to find out is whether either/both are still available in mechanical shifting or if they’re going Di2 only like their road siblings.


Yeah, the information we currently have is really anecdotal.
I would really be surprised if they didn’t make a 400 version, that’s mech only.

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I’ve been waiting for Shimano mullet for years. I’ve almost pulled the trigger on axs with the sram deals going on. Should I wait?

No one can tell you that. There are rumblings about an updated Eagle AXS too, but I cannot tell you if waiting is worthwhile or not.
If you are not in a hurry, I’d probably wait.

Didn’t Rides of Japan have a Dura Ace / XTR mullet setup before GRX even existed? I think it was plug and play too, no software hacking or whatever.

I wouldn’t, The current prices on AXS stuff is a killer value and the system works very good as well. Anything new will also come with the ‘new’ price tag. I’d buy AXS today in a heart beat vs waiting for new stuff.


Exactly what I’m doing! Picked up some Force AXS shifters and a Quarq power meter spider super cheap and I’m keeping an eye out for the rest.

Speaking of which … anyone know the largest cassette for a Force XPLR rear derailleur? I’m on the fence about Force XPLR or straight-up mullet with a mountain bike rear derailleur, but wondering if I can meet in the middle (something like a Garbaruk 10-48 cassette) with a non-flattop chain.

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You’ll want to run a flattop chain with any of the XPLR mech’s.

I honestly don’t see the appeal of XPLR. If I want 1x, just do a full mullet, if you want small jumps, do 2x.


or a small jump 1x with the classified system (getting that built for my gravel bike with Ultegra 12s - which will go on my road bike once the new Di2 GRX is released (didn’t want to buy into old tech incompatible with the new versions).

I might try to use it for climbs on a 2x setup for an ultra reduction (e.g. for the Marmotte to be able to spin fast)

Yes, Phil Gaimon also had a 1x11 mullet setup for one of his Everesting/hill climb bikes (34-tooth chainring and 11-40 cassette if memory serves).

The issue is that there is no 12-speed Di2 XT(R) groupset and 11- and 12-speed Di2 components are incompatible. So it seems that (1) Shimano (finally) releases 12-speed Di2 mountain bike groupsets within the next 12 months and (2) these are compatible with 12-speed dropbar groupset components.

XPLR has a few advantages: on a groad bike you can have one wheelset with the 10–44 cassette and one with a 10–36 cassette, the former being for gravel rides, the former for road rides. Also, for many applications a 10–44 cassette has more than enough range. We aren’t all as strong as the pros who pair this cassette with a 50-tooth chainring.

What for? I have SRAM Force eTap AXS with a power meter, and it works great.

Reasons to look forward to Shimano doing this:

  • SRAM is usually heavier than Shi
  • SRAM chains and 10t cassettes are less efficient
  • GRX gen 1 braking performance and hood shape are THE best I have ever experienced
    For 2x:
  • SRAM has a few issues here: the FD is not super reliable, on many frames the battery of the FD blocks the tire from being wider, and the SRAM force Wide, which offers more space here is really heavy and only has one chain ring combo
  • SRAM is limited to a 13tooth jump at the front. 46/33 and 43/30 are probably the most common for gravel here.
    Comparing this with the 48/31, it just offers the best of both world‘s really. High enough top end gear (52.5kph at 90 cadence on a 42mm tire), but super low bottom gear.

SRAM has a few advantages over Shi, but since you can use a Quarq PM and Sram cranks on Shimano, I am just more excited about a new Shimano, when it comes to racing.


I haven’t tried GRX, but have owned and tested various bikes with Ultegra (Di2) and Ultegra/105. My new bike has Force eTap AXS:

  • Braking on my SRAM brakes is leagues better, both in terms of lever purchase and brake feel. I’m not a Shimano hater, I really like Shimano’s MTB brakes, but all of their drop bar brakes feel wooden and bad to me. (Like I wrote, I don’t know how much difference the hood shape of GRX makes.)
  • I don’t think efficiency differences matter much in practice.
  • Regarding the 13-tooth jump in the front, I don’t think this matters. What matters is what gear ratios you get. And with a 10-36 cassette, you get more range than with Shimano’s current setup (48/31 and 11-34 cassette). The closer ratio in the front is probably an advantage since you have more closely spaced gears.
  • You are right that you are faster with a 48:11 = 4.36, but the difference between that and 43:10 = 4.30 is 1.0 km/h (52.5 km/h vs. 51.5 km/h). I’m not sure that this will matter in practice.
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How‘s that? The SRAM 12s chains have consistently tested 2-4 watts slower than Shimano XTR. That’s at 250W, which would be my target NP for something like a 4-6 hour event. As someone who races, why would I want to accept losing these watts?
This is disregarding the smaller ring and cog diameters, that make the efficiency even worse.

Gotta disagree here as well. Yes, the absolute range is bigger on SRAM, but for me, it’s about 3 things with gearing:

  • having an easy enough gear for the sharpest climb, and a tall enough gear for the fastest descent I encounter (SRAM wins)
  • having as small as possible jumps between the gears of the cassette to find the right cadence for the target power (Shimano Wins)
  • having the option to do a quick big shift in gears, so I can react quickly to varying terrain (undulating forest path, with sharp inclines and equally sharp descents). Here the bigger jump in the chain ring offers an advantage. You don’t need to shift up and down the cassette as much, but just shift the rings instead.

I for one want this to be a big jump, not a small one. For small jumps you have the cassette.

I am not saying it is a huge difference in speed. However, it is a huge difference in feel. Having switched all my bikes from AXS to 9200 (but the gravel bike), I do not want to go back to 10t anytime soon. The 10t cog is only a few watts less efficient than the 11t on Shimano, but man it feels and sounds draggy. Might be just me, but the 10t cog is great for range, not great for feel.


As someone who wants a new gravel bike I would look forward to DI2 Grx820. Esp if I can run a 50x34 in the front and 11x36 in the back. I have ran grx810 1x set up and 2x set up and thought both did a great job. The downfall of Shimano is limited availability. I know rival is almost the same weight and functionality of Red, which allows me to piece together a pretty bad ass build for maximin cost savings.

My 44x11 and 44x12 feel draggy. I dislike that feeling, but I am not in that gear often

Practically the other part is that SRAM gravel drivetrains are 1x focused. This is great for a casual bike, and for easy riding. But for racing you want efficiency. A SRAM 1X system can bleed almost 10-15w against a shimano 2x in worst case scenarios. To get an efficient system on SRAM it’s actually quite hard - you either need to run XX1 mullet with a Road front derailleur - and maybe a 52/36 front., or an etap MAX rear but lose the chain retention. That gives you a 1:1 at the rear (most 1x gravel drivetrains end up being 40-42 front and a 40-42t wide range rear).

GRX 815 (or the new 12-speed version), a dura ace front and a 52/36 (or 50/34) and a 36-38 rear gives you a) wider range b) smaller jumps c) chain retention d) lower cost and e) better drivetrain efficiency.


Because it is balanced out by other advantages. In my case, I hate the ergonomics of Shimano’s STI levers: the hood shape is all wrong, I don’t feel securely wedged in the bike in the aero hoods position, the mechanical levers swivel which is a big no-no for me and even after two weeks I’d misshift with the Di2 levers. I also wanted a first-class 1x option, which Shimano doesn’t offer on road bikes.

I don’t think Shimano has smaller jumps in the cassette. Its 11-34 11-speed cassette has no 1-tooth jumps between any of the gears, for example. Instead, the gears in the middle of the cassette are closely spaced, not ideal for fast gravel or road riding. (And IMHO for offroad riding irrelevant as variations in terrain and pitch make that less relevant.)

SRAM’s 10–36 cassette has three closely spaced gears. But arguably, I think a fairer apples-to-apples comparison is 48/31 + 11–34 Shimano vs. 43/30 + 10–33 SRAM. The spacing between gears of the 10–33 cassette is much closer (e. g. 5 cogs 1 tooth apart at the top end) than Shimano’s 11-34 11-speed cassette.

I believe you. However, the gear steps of my 10-36 cassette feel identical in practice to SRAM’s 11-32 cassette I had on my previous bike, sans the 11-tooth sprocket and with some additional easier gears. (I have a 42-tooth chainring, so the tallest gear corresponds to 50:12 = 46:11.)

I like a quicker cadence at speed, so I’m only in my 10-tooth cog when I go downhill and I am in overdrive, and then it doesn’t really matter whether it is less efficient or not.

No, that’s not correct. SRAM offers 1x and 2x options with virtually identical gear ranges. For gravel your options are:

  • 10–52 mullet setup vs. 43/30 + 10–36: both offer about 520 % gear range.
  • 10–44 XPLR vs. 43/30 + 10–33 cassette: 440 % vs. 470 % is still quite comparable.

You can also look at road bike gearing:

  • 1x 10–36 vs. 46/33 + 10–26: 360 % gear range

This isn’t accidental. SRAM gives riders the choice whether they want to go 1x or 2x. Most components are interchangeable.

I already run this setup with the current 11 speed groupset, 11-36 Sram cassette and 50-34 crankset. The Grx/Ultegra rx derailleur easily clear the 36 on the back, even though it is not officially supported.

You are stating these like they are universally applicable. I like the Shimano STIs better than any AXS STI. This is personal. The 2-4W slower chain is universally applicable. Everyone‘s SRAM chain is slow.

This thread is about 12s GRX, with the new 11-36 cassette that is already used for the 105 12s.

On that note…

This is NOT a Shimano vs SRAM pp measuring contest, but a thread about news and speculation about the new 12s GRX. Let‘s please return to that.