What is Shimano GRX? Our in-depth guide

People in the cycling industry and cycling community had been clamouring for Shimano to produce a gravel-specific groupset for some time. So, when Shimano announced the launch of their GRX range it was one of the most eagerly-anticipated product launches in recent history. What is Shimano GRX? What makes it so unique? Allow us to explain…..

Sometimes you see a trail heading off across the fields and think to yourself ‘I wonder where that goes?’ Or you just prefer to leave the road behind and seek the solitude of forest trails and bridleways for a few fun-filled hours. Well for this and more the gravel bike was developed, a bike that’s off-road capable, yet can turn its hand to road riding too.

Gravel bikes place different demands on a bike and rider. When riding over tougher terrain or in quagmire-like conditions you need a gear range to help you navigate your way through. Shimano took up the challenge and launched their gravel-specific GRX series, a groupset that has the gearing you need to maximise your gravel bikes off-road potential.

How to explain what GRX is…. It’s not that simple, GRX is a range of groupsets, well kind of. You see they aren’t the groupsets that we know and love, you know the ones where all of the components belong to that groupset exclusively. With GRX there is a crossover of components, this allows people to pick and choose what parts they wish to fit and guarantees inter-compatibility. So, what are the options?


The entry point to GRX is the RX400, rather than a single chainring it instead features a double chainring much like standard road groupsets. The two chainrings at the front and 10 sprockets on the cassette on the rear give you a total of 20 gears in total. This would put it on a par with Shimano’s Tiagra road series groupset which also offers 20 gears in total.

Where GRX400 differs markedly is in chainring size, it is equipped with smaller chainrings than you would expect to see on a road chainset. In this case, 30 and 46T, instead of a road compact 34-50, and when this is combined with an 11-32 road range cassette it offers a very low gear range indeed.


The next step up is the RX600 which is equivalent to the 105 road series. It is available in a single chainring or double chainring configuration for 1×11 speed or 2×11 speed gearing. The levers and chainset are RX600 but the rear derailleur and front derailleur (double) are taken from the RX810 series. The double setup again comes with 36-40 chainrings and an 11/32 or 11/34 road cassette. The single chainring is a 40T and comes with an SLX (MTB) 11-42T ratio cassette.


Move up again to the RX810, again this is available in a double or single ring configuration. The RX810 benefits from slightly lighter and more advanced materials which offer a more premium finish and lighter overall weight. The double setup uses an RX810 front derailleur and RX810 rear derailleur with maximum sprocket size of 34T. The single chainring system uses an RX812 rear derailleur which is compatible with cassette sprockets of up to 42T.

RX815 Di2

Yes, Shimano even offers GRX with their market-leading electronic shifts. Like the RX810 it is available with 1 or 2 chainrings and the rear derailleur will change depending on which one you choose. Di2 is fully programmable meaning that you can change how the system behaves. You can programme it to shift all the way up and down the block by simply holding a button in, shift singly and even swap which levers operates each derailleur. The other key feature is that after every shift the derailleur self-adjusts so there is no chain rub and the chain line always remains optimal.


GRX is available in a double configuration with 30/46 or 31/48 tooth chainrings, dependant upon which system you choose. It’s also available in a single ring configuration which is referred to simply as one-by (1x). Which you choose is purely down to personal preference but we’ll try and assist you in determining which suits your riding style/needs better.


Shimano has added some nice finishing touches to their levers which have in their own words ‘gravel inspired ergonomics’. Fancy words aside this translates into some seriously stylish and comfy levers. The shifter itself offers the same impressively smooth shifts of its road and MTB siblings. The lever blade features some radical new shaping, with a distinctive scoop that fits your fingers snugly when braking or simply when resting your hands on the hoods. The levers also benefit from a new textured anti-slip material which helps to provide more purchase when the terrain gets bumpy.

These levers also connect to some of the most impressive hydraulic disc brake calipers available. Providing superior control and stopping power over any terrain and in any prevailing weather conditions.


If you choose the 1x system then you can obviously ignore this section. The GRX front mech for the double system owes its design to the road range of derailleurs. Though the GRX derailleur is designed to accept a wider range of gears.


A GRX RX812 derailleur fitted to the Ribble CGR Ti; note the small grey lever next to the top pulley wheel. This is the on/off switch for the clutch/chain tension.

To better cope with the ever-expanding cassette sizes, Shimano has called upon their MTB expertise and applied their Shadow + design to the GRX series of rear derailleurs. Each derailleur is now equipped with a chain tension system (clutch) to prevent the chains from being unshipped over bumpy surfaces and also to help reduce chain-slap (when the chain bounces and chips the chainstay).


GRX utilises 2 types of cassette, the double system will use a narrower spread road range cassette in ratios of 11/32 or 11/34. The 1x system will be equipped with an MTB style cassette with a wider ratio of 11-42 or thereabouts.

Which should i choose?

Well….this is the million-dollar question, both have their pro’s and their con’s;

1x Pro’s

  • Weight– With only 1 chainring there’s no need for a front derailleur with its attendant cabling or the internals for the front gear shifter (marginal gains).
  • Maintenance – There are no words for how much of a pain it is to clean the front derailleur, behind the front derailleur and the rear of the chainset.
  • Gear adjustment – No front mech, no adjustment required (WIN).
  • No front derailleur – With the removal of the front derailleur there’s lee to go wrong mechanically. The chain cannot jam in a front derailleur that is not present nor can debris such as twigs or mud cause a chain jam.02

1x Con’s (you will note these are very minor)

  • Gear range – Because the cassette covers such a wide range of sprocket sizes the step up from one sprocket to the next adjacent sprocket get larger as you shift up the cassette. This is less efficient and can affect your pedalling rhythm, particularly when climbing.
  • Spinning out – Directly linked to the above, because the hardest gear you can pedal is only an 11-40T or 11-42T you will absolutely ‘spin-out’ on descents. (There will be no tension on the cranks so your legs just spin like the clappers).

Double Pro’s

  • Gear range – A 46 or 48T large chainring combined with a 30 or 31T inner chainring means that a narrower spread cassette can be fitted. Therefore the increase in the number of teeth between 1 sprocket and the next are smaller. This helps has less impact on pedalling rhythm when changing gear.


  • Weight – The extra weight of the chainring, front derailleur (including associated cabling) and internals of the front shifter add a small amount of weight.
  • Maintenance – Having that extra chainring and derailleur in place makes it harder to clean that area of the bike.
  • Chain jam – When riding through sticky off-road terrain it is possible for the chain to pick up dirt and debris which the lodge in the front derailleur and causes the chain to jam or to drop.
  • Gear adjustment – Gear cables need replacing and cables stretch causing more adjustment to be required.


So what can we conclude from all of this information?

Both the double and single ring systems have their merits and let’s face it there are no real downsides. When comparing the 2 we are looking for the most minuscule of differences. Both offer the extremely low gear range that you require when riding off-road and you’d be hard-pressed to be affected by this gear range when riding on tarmac either.

It boils down to this, do you feel the extra gears offered by a double system to be absolutely essential to your riding experience? Or would you prefer the simplicity of the single ring set up without the faff of having to adjust the front gear and the added ease of cleaning the 1x drivetrain?

  1. Interesting, I would like your opinion, I am thinking about a titanium frame, but I am undecided about groupset. I do most of my riding in the alps I ride on the road and have to climb a lot, I am heavy at 100kg so was wondering if the grx would be a good option as a groupset because I spend nearly all my time in the lowest gear of an 11 -32 cassette on ultegra? More help up the hills would be nice.

  2. Hi Grant – I have just got a gravel bike with GRX, but the road bike I have has ultegra. From the experience the GRX will definitely help you getting up the hills, i find myself not really needing the lowest gears on the GRX groupset, whereas I frequently use it on the Ultegra 11-32. You might find you run out of gears on the downhill, and cant get any power through.

  3. Hi!

    I’m wondering if you could elaborate on the differences between the GRX RX400 and Tiagra?

  4. Hi there, I’m building a tourer based on a Croix de Fer frame with flat bars, 73 this year so the old legs not as strong as they used to be! I’ve got a cdf with a compact set up at the moment, and no way can I go up steep hills with two laden panniers.
    The plan is, to use a GRX 46/30 on the front , and would like an 11/42 on the rear. I’d use a GRX FD RX810 front mech, with probably an slx or xt rear mech. Would this set up work please?

  5. Hi Pete,
    Thanks for getting in touch, we cannot see any reason why your suggested combination would not work. The GRX front mech range is 17 and a 46/30 combo is only 16 so this would be fine.
    Team Ribble

  6. I am looking to change bike – current ones has 105 2×11 -set up – I’d like the option to get into canal paths or cut down lanes/ bridle paths that aren’t tarmac surfaced but if I went say 40 front 42 rear how does that compare when climbing on roads where I’d be in say 34/32 gear. Would 40/42 be harder or actually easier due to being closer to 1:1 ratio? Looking at the CGR 725 and think 1X is the way to go

  7. Hi Rich
    Thanks for getting in touch,
    A 40/42T will be marginally easier than a 34/32 due to it being a lowe than 1:1 ratio. As a comparison, a 34/32 combo gives you 1.15 revolutions of the wheel for every revolution of the pedals. The 42/40 figure is 1.05 so as you can see is slightly easier. The main reason people choose a 1x gearset is the simplicity that it offers, the removal of the second chainring, and front derailleur makes maintenance simpler and eliminated the chances of debris becoming lodged in the mech and causing a chain jam. Personally, I always ask people who are torn between the 2 what sort of riding they are mainly to use the bike for. If it is almost exclusively off-road then a 1x is certainly beneficial, if it is mainly off-road with a little off-road action then the double may still serve you better. The jumps between sprockets are obviously going to be more pronounced at the top end of the cassette which affects pedalling cadence when shifting, leading to a loss of momentum. I have to say I say I use GRX 1x for commuting which involves both road and gravel and love the simplicity and haven’t found it too wanting but it is undoubtedly slightly less efficient when shifting at the top end fo the cassette so it is worth bearing this in mind. I hope this helps. Have a Great Christmas & New Year from all of us here at Ribble.
    [email protected]

  8. Thanks Alan and to date I’ve mainly done road riding but our roads are terrible and to answer your question I’d like to do more non road routes or mix it 50/50. I have a mtb with 1X so appreciate the benefits it offers. I’m moving towards 1X for the ribble cgr 725 my main concern is being able to climb rather than top end speed as tbh with the 2×11 I can only use smallest cogs on the rear cassette with the 50 chain ring when going down hill. So the aim is to shift my riding to more non road tracks or canal paths so think I know what to go for – appreciate the feedback

  9. Took delivery of Ribble Ti CGR about 2 weeks ago
    Spec 1 by GRX
    Pretty good combo but not what I wanted
    Quickly ordered Wolftooth 44 compatible chainring .Sunrace 11/46 11 speed cassette and with the aid of a goat link hey presto. One faster bike downhill , a bale out gear for them darn Chiltern Hills. Hey I’m 60 and need all the help I can get.
    Chain fitted fine
    Have to say the TI frame is a work of art and glides over the road with Conti 49 mm G Allround Tyres Purchased a spare set of Wheels and with the same cassette set them up tubeless with Conti 5000 to
    But of fun setting all the tyres up tubeless but getting there . Bit of trial and error Decided for winter to run with the 40 mm tyres
    In the process of applying helicopter tape and looking forward to putting a fair few miles under my belt
    Damn it I had to wait nearly 5 months for the bike to turn up but it was worth it
    Any way if you want to run a bigger rear cog , dead easy and it works
    I had this set up on a bike I converted from a Sora 9 speed double for approx £240 Works like a dream and convinced me at least the FD is dead
    Enjoy 2021 which hopefully will allow us to roam far and wide

  10. Hi Graeme, thanks for getting in touch and we hope you have a Happy New Year. I like what you have done here, the same gearing but a larger chainring for better performance on the flat and when descending. I too went with a tubeless conversion on the CGR 725 steel and as you say it is a bit of a faff to get the tyres seated correctly but they are so comfortable and fast-rolling it is well worth the effort. Enjoy your lovely new bike and we’d love to see some piccies whilst out on your travels. Share to Facebook, Twitter, or Instagram and use the #myribble. Best Regards
    [email protected]

  11. Are ribble likely to offer the 1by? On the Ti, it only seems to offer the 1by option.

  12. Hi Luke,
    Thanks for getting in touch, we only stock the 2x version of GRX in the RX400 2×10 speed option. All our other GRX options are the 1x variants.
    Best Regards
    Team Ribbble

  13. Nice piece but I should point out as a former magistrate that footpaths, no matter how tempting, are for pedestrians and not cyclists. I assume you meant to write ‘bridlepath’.

  14. Hi James,
    Many thanks for getting in touch and pointing out the error. In no way would we advocate riding on pavements, the blog wording has been amended.
    Best Regards
    Team Ribble

  15. I have used the RX400 for 6 months now, and really like the design concept. The brake levers and hood design among the most comfortable I have used. The gear ratios are great for most of what I can actually ride, including single track, the clutch does what it says (i.e. works) and the brakes are solid. My only gripe is the moving parts are just less refined than I had hoped. Fine for canal path commuting but anyone with more adventurous trips planned will feel the impact on overall function. My next upgrade will be RX600 or better. Now for the heresy, my setup has a 10sp cassette which is pretty rugged and I am impressed how much dirt it can handle, honestly I have never felt need for 11sp on mixed surfaces. I would like to see 10sp option extend to the higher versions.

  16. Hi David,
    Many thanks for taking the time to comment on the blog. Your feedback about GRX pretty much reflects the Shimano groupset hierarchy. RX400 is the entry point into GRX and is roughly equivalent to the Tiagra 10-speed road system. GRX600 = 105 11-speed and GRX810 = Ultegra, the general rule of thumb being that the higher you move up the ladder, the more advanced the materials and technology that make up the components become. So, while RX400 is a highly capable groupset it does quite have the same level of refinement or build tech as its higher-level siblings. They will certainly not extend 10-speed options as this is regarded as a backwards step with competitors already offering 13-speed options. The industry is always looking at ways to offer more gearing options, not less. Even if we deem them necessary or not! Best Regards [email protected]

  17. Hi Jeffrey,
    Thanks for getting in touch,
    It’s a difficult one to answer without knowing what 2×11 speed setup you are running currently. If it is a standard road setup, then the answer is, no you cannot fit an 11-42T cassette with your current rear derailleur. To cope with such a large cassette you would also have to swap out your current rear derailleur for one that is designed specifically to cope with a 42T max sprocket, such as the GRX RX812 https://bike.shimano.com/en-EU/product/component/grx-11-speed/RD-RX812.html. I hope this information helps.
    Best Regards
    [email protected]

  18. I’m having issues on my turbo trainer with my 1×11 setup and using a Deore 11-42 cassette. It’s smooth her ally but the middle few rings are looking to change all the time. It doesn’t seem to change, no matter what I do to the mech limit screws or the cable tension. Odd. Annoying.

  19. Hi Dave,
    Sorry to hear that you are having issues with your setup. I’m afraid it is outside of my area of expertise, my best suggestion would be to check with the ‘Ribble owners on Zwift’ Facebook group who are more familiar with the specifics of various trainer compatibility and setup issues. Or failing that, maybe ask the trainer manufacturer themselves to see if they can advise if your exact setup might need some tweaking to work correctly.
    Best Regards
    [email protected]

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