Shimano GRX 12s (2023/ GRX820/610)

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.


I started my sentence with “In my case, …”, which means I was speaking only about my own preferences, not something universal. But you did ask why someone would choose SRAM over Shimano, and I think ergonomics and 1x vs. 2x are two good reasons. I wanted my next road bike to be 1x and I vastly prefer SRAM’s ergonomics on dropbar bikes. Other people prefer GRX STI levers to Ultegra or DuraAce STI levers. My point is simply that ergonomics and gear choice are factors, not that everyone has to agree with your or my choices.

Even then I don’t think Shimano’s cassette has tighter gearing. SRAM offers you one more tightly spaced gear at the top end at the expense of one more large jump on the climby end. Shimano and SRAM made the same tradeoffs with their 11-speed cassettes, too. (Even when I had a Shimano groupset on my previous road bike, I did replace my Ultegra cassette by a Force cassette.)

Sure, and I am not a SRAM zealot. I’m very happy with my XTR drivetrain and XT brakes on my mountain bike :slight_smile:

Is there any word whether Shimano will still only offer the few gearing options that are rumored? Is there talk of a GRX 1x12 cassette for gravel riding?

No. XPLR is 1x only.

You must be thinking of WIDE, which is the direct competitor to gravel GRX 2x.

The issue is you still end up running a less than effective chainline, whereas GRX is happy with an ‘almost road’ 52/36 front 11-36/38 rear.

This allows you to spend most of your time at the speed you might ride in a gravel race paceline (or, on the road training) in the ideal part of the cassette and front rings for optimum drivetrain efficiency.

Plus you get 4W from it being Shimano.

Hopefully this will remain the same with 12sp GRX.

But didnt you say you havent even used the grx shifters? The di2 hood shape is completely different from other shimanos

1 Like

Shimano: 11-12-13-14-15-17-19-21-24-28-32-36
SRAM: 10-11-12-13-15-17-19-21-24-28-32-36

So literally the only difference is SRAM has a 10t cog to offset the small chainring or in other words: offer greater range. While Shi has an additional 14t cog.
If that matters to you or not is personal. I don’t like using the the 10t, so that’s not really a bonus for me.

The good thing for the consumer is, that they’ll now have an additional choice, without sacrificing the 12th gear.
I agree that SRAM has the more compelling offering for most gravelers in the current gen. But they could really improve a few things as well.

1 Like

Can you run the quarq dfour with the 12s shimano rings?

1 Like

And the mullet setup uses a mountain bike RD. We all know that.

You are missing my point: SRAM gives cyclists the choice whether they want to go 1x or 2x without them sacrificing gear range. The WIDE RDs aren’t 2x only either, you can use them 1x or 2x. (I use a Force WIDE rear derailleur on my 1x road bike.)

True. Yet pros like Keegan Swenson opted for a 1x (mullet) setup in some races (such as UB, which he nearly won). That’s because 2x has drawbacks, too, and on balance I don’t think there is a clear winner, it is mostly a matter of personal preferences.

When it comes to gravel bikes, the community seems quite evenly split between 1x and 2x. SRAM arguably offers more options than Shimano here (e. g. in terms of chain ring sizes and cassettes).

Right, I have tried many different Shimano STI levers (RS505, Ultegra 6800, Ultegra 8000, Di2), so I don’t know whether I’d be happy with the GRX hood shape. But button placement and lever action are identical to the on-road variants, i. e. for mechanical GRX groupsets the brake lever still swivels and the Di2 buttons are still the same.

On paper, Campag’s Erkar would have been a great fit, but I just don’t like their index finger + thumb button layout.

Again, it is less about my personal preferences and more that ergonomics is and should be a factor when deciding which groupset to go for. On the mountain bike side, I don’t care, I get along with SRAM groupsets just as well as with Shimano’s.

I don’t think “because pros” is a very good justification. I don’t disagree you have more options, I just don’t care about the options for my use case. I forgot to add you probably lose a few watts to the size and protrusion of sram hoods vs grx that almost outweighs any aero gains from no FD (I think josh from silca was joking about this recently).

You have a point. However, I just wanted to say that pros have thought about the pros and cons of 1x vs. 2x much more than we have, and for them marginal gains are much more important.

That’s totally fair. Like I said, I prefer SRAM’s line-up, because it gives the 1x and 2x community pretty much equivalent options with an easy to understand compatibility matrix. Shimano’s is a mess and gives cyclists many fewer options. If you prefer 2x, you have plenty of options. E. g. in addition to the 10–33 cassette (which has the same range as Shimano’s 11-36 cassette), you can get cassettes with more or less range if you wish. SRAM has 4 cassettes that are compatible with its WIDE rear derailleur, plus 3 more that are 1x only (10–44, 10–50 and 10–52).

It is clear that Shimano’s road and gravel groupsets are designed by different teams that don’t seem to be talking too much to each other. It seems that they want to make it difficult for people to mix and match components. I know roadies who prefer the shape of GRX levers, but currently can’t put them on their 12-speed road bikes. (I reckon, living in Shimano land, that the road groupset team has the most prestige inside Shimano, a distant second is its MTB groupset and then comes gravel. I mean, how many years has it been since Shimano has released 12-speed MTB drive trains and we still don’t have 12-speed Di2 mountain bike groupsets!?!) If I were Shimano, I’d release way more chainring options than just 40 and 42 teeth for their 1x crank, for example. SRAM offers 38–54 (or 56?) in 2-tooth increments.

I don’t find that very convincing. Plus, I don’t think this is true in practice: the biggest bit of aero drag is the sack of water we call our bodies. I am pretty sure I am more aero on the bike that allows me to spend more time in an aero position, not whether the hoods by themselves are more or less aero.

I am much more comfortable in the aero hoods position on my SRAM-equipped bike than on my previous Shimano-based bike. My Shimano levers had fatter, but less tall knobs, so a road imperfection could knock me out of my aero position. Newer Shimano groupsets are better, and perhaps GRX is better still, but I very much like the size and shape of SRAM hoods. (It isn’t the bike fit, I have had quality bike fits, and the fits of my old and new bike are equally good, modulo differences in geometry.)

I’m not saying you have to share my preferences, my point is simply that ergonomics matters when picking a groupset.

Regarding aero gains of 1x, I don’t think I mentioned the absence of the FD as an aero benefit. If there is an aero benefit, I reckon it is quite small because the air in that region must be super turbulent from those stupid legs that keep on circling around in that region :wink: I think the biggest gain is that the lack of a FD gives frame designers more freedom and allows for more tire clearance.

Plus, a lot of riders don’t like shifting chainrings. Most roadies I ride with (and myself included when I was on 2x), we’d stay in the big chainring as much as possible, and the chain line must have been less efficient as the chain angle is more extreme. That’s why I kept my 11–32 cassette and opted against a 11–28 cassette: on the latter I didn’t want to use the 50:28 gear combo whereas with the larger cassette, I could and did get away with it. That was quite useful to get over some short kickers, bridges and climbs.

Friction Facts tested brand new UFO treated chains in the test you’re referring to. The longest runtime was 13 hours. While the SRAM chains started out less efficient, by hour 13, the Dura-Ace 11-speed chain and YBN 11-speed chain began to lose efficiency while the SRAM Force 12-speed flat-top chain was still getting more efficient. At hour 13, the difference between the DA and Force chain was .64W.

It’s known that SRAM chains are manufactured to tighter tolerances, which may result in additional friction when new. However, I wonder how efficient they run after 100 hours of break-in where the sliding surfaces have been allowed to polish each other.


You might be correct here. Idk. I get all my chain friction information from Adam Kerin (aka. zero friction cycling) and he clearly states that an XTR chain hardly has any wear at all when maintained correctly, so it should not become slower. Also, he has tested the XTR chain at 3.8W vs 6.7W for the Flat-Top, as an average over thousand of kilometers. Idk who is right or wrong here. The smaller diameter of rollers, and much higher drag out of the box are definitely not for me.
And shifting is worse (slower, less reliable, more difficult to set up) too. That’s at least for 9200 v AXS. We don’t know how this is for 820.

Can we have nice things on the internet and stop the useless Shimano / SRAM opinion battle and get back to a discussion of a potential new GRX 12s group set?


Is there going to be a non-mullet 1x12 option?

Shimano’s 10–45 cassette isn’t really comparable to SRAM’s 10–44 cassette, the former has MTB gearing with tightly space climbing gears (not really popular as far as I can tell), whereas the latter has tightly spaced gearing at the top.

And is there going to be a 11–40 or 10–36 2x cassette option?

Flat-top chain rollers are larger in diameter. Kerin also doesn’t do efficiency testing, at least not in-house. He usually relies on Friction Facts for that data.

If you check YouTube, rifling through the cassette on AXS is actually slightly faster than Di2.

Anyway, there will be an RX820 2x RD, but it’s unknown whether they will offer cassettes with a 10t for it. We’re about to see Shimano introduce a fourth 12-speed freehub in MicroSpline Road in addition to HG, HG-EV and MicroSpline. I frankly find it odd that HG-EV even exists considering exactly zero other brands have adopted it.

I am not talking about roller size, but size of the rings and cogs. It’s an 11-36 for 2x GRX 12s.

I thought the latest 12s Road freehub was just about future-proofing with double the splines in case they want to update cassettes in the future to reduce how much they chew into freehubs? Shouldn’t that (either HG version) plus the existing MicroSpline cover everything the new GRX needs to do? Do we have any indication that they’re even planning to introduce anything additional?

Yep, currently I would stick to HG(road 11s) for 12s because the HG-EV freehub only works with 12s road but all the 12s cassettes are backwards compatible. I think that in addition to shimano, DT Swiss also offers the HG-EV freehub

I asked this question here, too, but it seems the answer is unfortunately no (at least when it comes to first-party cassettes). I reckon Shimano has two options: either something like a 10–36, 10–40 or 10–44 cassette that uses Microspline. Or a 11–40 12-speed cassette. The latter would have the same range as SRAM’s 10–36 cassette. (The range of Shimano’s 11–36 cassette matches that of SRAM’s 10–33 cassette.) Since Shimano (theoretically) makes a 2x12 mountain bike groupset with a 10–45 cassette in the rear, we know they have the derailleur technology to make a 2x GRX setup work with a 40-tooth cog in the rear. (I only write theoretically, because I have never seen or heard of a bike in the real world that uses its 2x12 mountain bike groupset.)

1 Like

How often are you using it, though? I’m pretty much only using it when I go downhill, so not often. So not a huge factor for me. The extended range afforded by the 10-tooth cog is something I take advantage of on every outdoor ride, though.

YMMV, though perhaps.

Definitely. Here are a few things I’d like:

  • Add a 10-39 or 10-40 cassette. That’d be great for road riding and gentle gravel riding.
  • Reduce the number of rear derailleurs to 2: a regular one with support for up to the 10-40 cassette mentioned above and a 1x-only rear derailleur that accepts 10–50 to 10–52 cassettes.
  • Offer cranks with even smaller ratios. E. g. adapt a mountain bike crank. Bike tourers and others would appreciate this.
  • Offer a native power meter solution for the 2x gravel crank.
  • Extra programmable buttons built into the shift levers. That’s one feature I’d like SRAM to copy from Shimano .

Do you have any other suggestions?