Shimano GRX 600 groupset

Shimano's GRX 600 groupset is an excellent way to breathe gravelly life into an old (or new) wide-tyre-clearance frame. With typical Shimano attention to detail it's delivered a groupset that works brilliantly in any weather or terrain, and evolution will no doubt sort out the current shortcomings.

• Pros: Excellent braking and shifting in the grottiest of off-road conditions, compatibility with many other Shimano products
• Cons: Limited 1X gear ranges, no post-mount calliper option, only two quite large chainring options

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• FC-GRX RX810-1 chainset
• RD-RX812 rear derailleur
• BR-RX810-F brake calliper
• ST-RX600R 2 x 11-speed dual control lever (right)
• ST-RX600L 2 x 11-speed dual control lever (left) + BR-RX400-R brake calliper
• HG701 chain
• Shimano XT CS-M8000 11-40-tooth 11-speed cassette
• Complete groupset

Shimano's GRX 600 1X groupset represents a validation by the world's largest groupset manufacturer of the fact that 'gravel' is not a fad, it's here to stay as people move towards cycling in a safer, more scenic, low- or no-traffic environment. The company has finally embraced the public desire for better performance and more options when taking drop-bar bikes off road.

Much has been written about the tech specs and pricing of GRX, summarised at launch by Dave, and there's a large selection of GRX bikes now available, starting from as low as £1,300 equipped with this GRX 600 1X groupset.

Test setup

To test the groupset I fitted it to a 2016 Boardman Team CX bike – originally £999, fitted with SRAM's workhorse Rival 1X hydraulic groupset. It's a great alloy frame with gravel-friendly touches like two bottle cages, mudguard/rack mounts and tons of tyre clearance.

My first challenge with fitting GRX was the frame and fork having now-almost-obsolete post mount callipers. GRX brake callipers are rebadged Ultegra and are flat mount only, and no, there's no way to put a flat mount calliper on a post mount frame/fork (though you can put a post mount calliper on a flat mount frame).

A benefit of Shimano's thinking is that many components are interchangeable, and I was able to use the BR-RS785 post mount callipers with no issues at all. You can buy the 2X 600 levers as a pair, but not the 1X set, so if you need to go the post-mount route you'll need to order the brake-only left and brake+rear-shifter right separately, with your callipers of choice.

The RX810 1X chainset comes in only 40 and 42-tooth flavours, and because it's 1X it can benefit from thick-thin alternating tooth profiles, greatly assisting chain retention. GRX matches it with an M8000 XT cassette in either 11-40 or 11-42 ranges. There's an 11-46 on the GRX page, but the GRX long-cage rear mech is limited to 42T max. So if you stick with GRX, you've got a lowest gear of 40x42, or the roadie equivalent of a pretty spinny 34-tooth small ring and 11-36 cassette. As it's Shimano, many Hyperglide-compatible cassettes are possible, including Ultegra and 105, which helps to keep running costs down.

Shimano originally sent me the 42T chainring and 11-40 cassette, but I found that just a bit too high-geared for the often 10-15% gradient hills where I ride. Swapping to a 40T chainring and 11-42 cassette made a world of difference, the extra 10% or so lower gearing enabling long, seated climbs; it would definitely be the way to go with luggage.

The RX812 dedicated 1X rear mech has a clutch to keep chain tension high, avoiding chainslap and dropped chains. The clutch has an on-off switch which reduces the shift effort needed when off, but to be honest it's hard to tell the difference at the lever end so I left it on all the time. Coming from a SRAM setup, one obvious missing feature is no cage holder mechanism, to remove tension by swinging the cage forward to facilitate easier wheel removal and installation.

Installation

There were a few foibles during the install process, with the levers posing some questions. The left-hand brake-only lever didn't come with the required flange bolt to secure the brake hose, which is a new larger design. The bolt was included in the GRX flat mount calliper box so fortunately I had one to hand, but if you were buying the lever separately from the post mount calliper you might not get the right size flange bolt included. You'll be needing the Y8AL98020 flange bolt kit.

I had a media-release GRX setup and not the final consumer version, so had to do a full oil install and bleed. When you buy GRX, the lines and levers will come with oil installed and everything ready to go – just cut the brake hose to the right length, remove the bung from the lever, insert and tighten the flange bolt. If you're mixing and matching outside the GRX family, you might want to triple-check you have all the required bits to hand. Leave the lever only loosely attached to the bar in the correct position as you'll likely need to remove it to tighten the flange bolt once you've got the hose length correct.

Matching up the calliper and levers was standard Shimano bleed procedure, but be warned you need the new ST-R9120 plastic adapter (£5) to connect your oil reservoir to the lever bleed port, which – like the flange bolt – is now larger than previous bleed port threads.

The RX600 levers have lever position adjustment but no 'free stroke' pad-bite adjustment, which is reserved for the higher-spec Di2 Servo-Wave-enabled models. Doing the bleed process properly delivered perfectly good lever feel and bite point for both brakes.

Installation of the 1X crankset was painless. The GRX crankset chainline is set 2.5mm further out to help accommodate wider gravel-friendly tyres, meaning you must use the GRX-specific front mech if going 2X. My bottom bracket is actually a PF30 with adapters to run 24mm Shimano cranks, and I have 5mm of spacers to play with. I chose to put them on the non-drive side to take up the gap and move the chainline more central to the cassette in the more-used lower gears. Given how much time I spend out of the saddle and my mileage split between different bikes, this tweak isn't a biggie, and the chainline shift quietened things down in lower gears which is where I spend a lot of my hilly time.

There's talk on the internet about the extra 2.5mm of chainline equating to an increase in Q-factor (pedal spacing) of 5mm over 'Shimano 146mm standard'. I measured the GRX pedal spacing as 151mm. My set of bog standard Shimano RS500 non-groupset cranks measure almost the same, maybe 1mm of difference, if that – so Shimano road cranks clearly differ if 146mm is common. Anyway, the distances we're talking here are nothing of huge concern.

GRX in use

The assorted technical angst and somewhat-restricted options disappeared out on the gravel. The most noticeable advantage of GRX is the hood and brake lever design, and by crikey it's a hands down winner. Based on the Ultegra R8000 lever, the GRX 600 lever is roughly the same shape, with three critical differences: the rubber hood material, the lever pivot point and the lever shape/material (noting that the higher-spec GRX levers are a different shape again, with taller hoods and Shimano's 'Servo-Wave' mountain bike brake technology).

Shimano claims the braking of the 600 levers is on a par with Ultegra, and I can't disagree. I never needed more than a finger, maybe two at most on really long descents. A grippier rubber hood means you feel totally connected to the lever even in rain and with muddy paws, and the deep indentation at the top of the lever gives your index finger a solid home. The lever itself has a rubberised finish that adds to finger grip.

Finally, the pivot point is shifted up so it falls above the knuckle of your index finger instead of under it. This means you can apply force to the lever more easily with your index and middle fingers.

Shimano has clearly done a lot of homework here, with the result that I never felt out of control on the hoods, bombing along stretches of very rough, rocky or rooty singletrack, bare-handed or wearing thick gloves. I run a reasonably wide Genetic D-riser bar with 420mm between the hood centres, and the combination with the RX600 levers was nothing but comfortable and confidence-inspiring. I only ever went into the drops for long flat sections where being a bit more aero was of use, and again it was easy to get one finger hooked on the lever for confident control.

The shift feel is typical Shimano – less positive than SRAM DoubleTap, but never found wanting. The slick inner cable and standard SP41 outer stayed smooth throughout the review, only needing the usual half-a-barrel tweak after a few hundred miles as the outer casings settled into place.

The combination of the clutch and alternating chainring tooth profile meant no matter what I tried, the chain stayed put and almost totally silent. There were a few sections where I managed to get a bit of slap going on over large rocks or roots, but this was in the 11T sprocket through silly-rough sections. On flat gravel at any speed/cadence/in any gear, the clutch worked its magic.

The limitation of an 11T smallest sprocket was not the issue I suspected it would be, coming from SRAM. Generally, by the time I'd wound up to the point I needed 40x11, I was already doing 43kph at 90rpm and trying to push a lot of air out of the way. A 10T shifts that speed up to 47kph – ie not much in the great scheme of things – if you really want it, spin faster.

Conclusion

Overall, the GRX experience is one of trust. Based on my experience, it's going to shift with typical Shimano 105-or-better accuracy, and the chain isn't going to fall off unless you do something rather spectacular. Your hands are going to stay put on the hoods, and your fingers will be able to brake and shift even when cold, wet and muddy. When something wears out you'll have a load of options for replacement. If your needs change, it's likely you'll find a compatible alternative for a component at a decent price.

> Beginner's guide to groupsets

Shimano has hit a home run with GRX 600. It's affordable, easily upgradeable, works with many other Shimano components and most of all works out on the road or trail to deliver a flawless shifting and braking experience in the worst of weather or trail conditions. You have the option to install 'interrupter' hydraulic brake levers on the tops if you want to brake from there as well, and as with all Shimano brakes they use mineral oil – a more environment- and workshop-friendly alternative to SRAM's DOT-5.1 fluid. If you really want to push the boat out, Shimano does a dedicated left lever that can operate a cable-pull dropper post, for the tidiest step possible.

No doubt we'll see wider-range rear mechs and 1X chainrings appear, further broadening the scope of terrain and luggage you can tackle without upgrading an entire groupset. It's this typically Shimano system-thinking that makes GRX a good investment. If you start now with standard GRX on a post mount frame/fork, in a few years you can upgrade to flat mount callipers and maybe a dropper post lever, maybe a different chainring or rear mech capacity, without losing your shirt.

Verdict

Affordable, easily upgradeable, compatible with many other Shimano components and works on road or trail