TESTED: Shimano GRX 12-speed gravel group set

Gravel is exploding around the world, and if you haven't really experienced at all don't fret – as you probably already have to some extent. The heart of gravel riding is about escapism and being in the outdoors. From riding long adventures, to exploring new places on whatever adventure you can manage. It has often been said that the ideal gravel bike is whatever bike you have right now. For some riders gravel will be a gateway drug to riding trails and getting into mountain biking, for others it will complement the mountain biking they already do.

Of course, gravel bikes exist as the varied demands of gravel do dictate that some specific equipment is advantageous. The position, wheelbase, gearing and tyre constraints of a road bike don't cut it, and most modern mountain bikes end up too heavy and undergeared. Interestingly, a 29er hardtail from about 5 years ago is still a good fit for wild and wooly gravel adventures given the gearing, weight and tyre clearance.

Thinking about gravel? Check out these bike reviews:

Trek Checkpoint SL6
Polygon Bend V9X
Genesis Fugio 30

As the performance needs of a gravel bike have continued to widen, so too have the bikes themselves, with clearance for wider tyres, more reach for stability, slacker head angles, and even suspension forks and dropper posts! In September 2023 Shimano released their second generation GRX range, with 3 different group sets at the 800 level, all offering 12-speed cassettes, huge gear ranges, better braking and improved ergonomics.

Offering 1×12 options built around both 10-51t and 10-45t cassettes, Shimano brought their slick shifting HyperGlide+ cassettes and chains to the gravel realm. But they didn't turn their back on double chain rings, and I was sent a 2×12 group set for review, along with new carbon RX820 wheels from Shimano.

A closer look at GRX 12-speed

Shimano's move to 12-speed with GRX follows the mountain bike group sets in 2018, and top-tier road group sets in the recent years. More than an extra sprocket, the addition of HyperGlide+ creates shift ramps to keep the shifting faster and more secure for shifts both up and down the cassette. Shifting is faster, and the 12-speed chains also have a far longer lifespan than the 11-speed models.

Shimano have updated the rear derailleurs of the 12-speed GRX equipment to suit the specific drivetrains, so the one I have on test is specifically for 2×12, with an 11-36t cassette maximum. This is paired to the cranks with a 31/48t chain ring mix, for a wide range of gearing.

Of note, while 11-34t cassettes have the HyperGlide+ ramps, the 11-36 models come from the Shimano 105 road range, and do not have the ramps.

Shimano also updated the shifters, so they suit flared bars with greater comfort, and for those using a 1×12 setup you can get a left hand shifter that is optimised for use with a dropper post. This setup is optimised for use with a front derailleur, and that has been changed to work with wider chain lines for more tyre clearance. Along with calipers that have greater clearance for the rotors (and therefore mud) most items have had subtle but important changes.

The new RX870 wheels from Shimano are all new, with a 25mm internal all carbon rim, laced to cup and cone bearing hubs which can have a freehub swapped from LG1 (for HG free hubs) to Microspline, for use with the 10-51t or 10-45t cassettes. They're light at about 1460g, and with a 30mm rim height they should be fast at speed and supple enough on rough terrain.

On the gravel

With this new release on my radar, I built up a Factor LS gravel bike in autumn, with current generation 11-speed GRX equipment in a 2×11 setup. I used it for a few big gravel rides along with week in, week out rides, and had it equipped with a complet 12-speed group set from Shimano, for this review. This included the 11-36t cassette and the new RX870 wheels, and Shimano's new CL rotors which you will see throughout their range for road, gravel and mountain bike use.

Like most changes to Shimano's group sets, the impacts of a shift to 12-speed for GRX are subtle and appreciated. The minor changes to how the shifters sit on the handlebars, and a change in profile for the rubber hood profiles are important. This is exactly where you spend the majority of your time. I also have found the hoods feel more secure with better grip and I'm more likely to descend in this position, compared to going to the drops. I also feel the lever throw for a shift has a faster actuation, therefore requiring less aggressive movements inboard. This will make a bigger difference for anyone with smaller hands, but not as much as Shimano's Di2 shifting – which hasn't arrived for the 12-speed GRX at this point, it is all mechanical.

Chain stability with Shimano's clutched Shadow Plus derailleurs has always been excellent, and that remains the same with the GRX 2×12. Even over washboard sections of dirt road, on singletrack and on rutted trails the chain was secure, even if I didn't feel secure myself! The front shift is dialled, as you would expect from Shimano. My own shifting wasn't as perfect as I had hoped, but this was traced to a flexy derailleur mount on the Factor LS frame. The cranks are the same as the 1x group set uses, so if I was to change to 1x I'd need a new rear derailleur, chain ring, cassette and freehub for Microspline.

The changes in the brakes are small, but important. Greater clearance meant I never experienced disc rub, and the new rotors change how the floating alloy carrier works with the stainless rotor. There was no heat warp, even using 160mm rotors and small 2-piston brakes on 600m descents. Given these rotors come in sizes up to 203mm, I'm keen to try them on my mountain bike too.

The wheels have been a revelation, given how smoothly they roll and their low weight. Shimano have quietly stepped out of the performance off-road wheel game in mountain bikes, but their full carbon rim and hubs with interchangeable freehubs suggest that we may see more action from them off-road in coming years. These rims are taped and setup tubeless easily, with zero burping, zero noises and just consistent solid performance for the 6 weeks of testing they had.

Verdict

I have put about 600km onto the new Shimano 2×12 group set. Perhaps the best feature is how it just blurred into the background. Moving from the existing 2×11 equipment to the latest 2×12 has small changes that won't appear that flash, besides the wheels. But on the bike, the subtle changes in comfort and ergonomics really add up, as did the changes to the brakes and rotors. I have always been happy with the performance from 2-piston Shimano brakes, but getting zero drag or rotor warp even when putting a lot of work through them is a nice change.

In terms of the 2×12 equipment and gear range, I'm on the fence. I think Shimano have limited one of the best attributes of their 12-speed equipment by not offering the 11-36t cassette with HyperGlide+. The shift performance, specifically how quickly it helps the chain moves across the cassette makes for faster and more secure shifts. This is available at a Deore level in the mountain bike group sets, and I think many would appreciate it in an 11-36 cassette for 2×12, and potentially a wider range cassette for 2x as well. Many riders will love the wide range 1×12 options, but for those who prefer 2x they may not be served with a low enough gear for loaded bikepacking. I didn't expect to use a 31×36 gear but did many times on a one day gravel ride which I don't even consider to have very steep climbs.

That aside, Shimano have improved on what is already a versatile group set. The fact that it remains mechanical is fine by me, as this is a group set range that serves a very wide user base, and it is simple to look after – especially on multi-day adventures. Shimano has suggested that Di2 is coming, but didn't give any dates. To me this only speaks to the versatility of GRX. Given the options in 1×12 and 2×12, I am certain that Shimano GRX will be seen on anything from all-road bikes to drop bar adventure rigs using droppers, suspension forks and 2.4” tyres. This is a versatile range that is bridging the gap between pure road and pure mountain bike use. And that's a space where a lot of riders spend their time.

RRP: Approx. $2000 as tested, wheels $2199
From: Shimano Australia

Hits:
– Improved comfort and ergonomics
– More options across all 12-speed group sets
– Better braking and shifting
– New era wheels from Shimano

Misses:
– Some 2x riders will want more range
– Mechanical only – for now
– No HyperGlide+ on 11-36 cassettes