Shimano GRX: World’s first dedicated gravel groupsets

by Dave Rome


If you ever wanted proof for how big the gravel segment has become, this is it. It’s been a long time coming, and Shimano has finally answered the prayers of many by announcing groupsets dedicated to gravel.

With wide range gearing options, 10 or 11-speed in 1x or 2x, Di2 or mechanical shifting, optional in-line brake levers, some clever ergonomic upgrades and no new freehub or bottom bracket required – Shimano may be late to the party, but it’s arrived in style.

Where new groupsets are traditionally launched at the top end, Shimano has launched GRX for the masses. GRX spreads across three levels which can be mix-and-matched, topping out at an equivalent to Ultegra Di2.


A bowl of road, and a spoon of mountain

Merging features of Shimano’s mountain bike and road groupsets together, Shimano’s new GRX is the world’s first dedicated gravel component offering. It’s not a wholesale departure from what is already available, but components have been modified and adapted to perform better on drop handlebar bikes when riding mixed terrain.

Story Highlights

  • What is GRX? Shimano’s dedicated dropbar component series for gravel and adventure riding.
  • Key features? Wider gear ranges, overhauled brake lever and hood ergonomics, offset chainrings, clutch-equipped rear derailleurs.
  • Gearing options? 2×11, 1×11, or 2×10. Existing road cassettes are used for 2x setups, and mountain bike cassettes are used for 1x.
  • Unexpected things? Optional inline hydraulic brake levers and dropper post remote.

Shimano’s road groups have long been equipped on gravel, adventure and cyclocross bikes, but not without limitation. The latest generation of Shimano Ultegra solved a few complaints by including a wider 11-34T cassette, improving front derailleur clearance and then later introducing a clutch-equipped RX rear derailleur. But it still felt like a road groupset, and even lower gearing was desired by many on dedicated gravel machines – forcing bike brands and riders to choose aftermarket cranks. GRX answers this, and more.

GRX components will be offered in three series: RX810, RX600 and RX400 – all hydraulic-disc brake. RX810 and RX600 are both 11-speed and can be set up in either 1x or 2x chainring configurations and with full cross-compatibility between price points. The budget-minded RX400 is a 2×10-speed series, with the OE (original equipment) market in mind and shares a few components with RX600.

GRX RX815 Di2. 11-speed with 1x or 2x options.

At the RX810 level, there is the choice of either mechanical or Di2 shifting, with the former designated by even numbers (e.g: RX810 and RX812), and the latter by odd numbers (e.g: RX815 and RX817). The new RX815/817 Di2 uses the existing Di2 e-tube interface, batteries, and wiring, and is, therefore, an upgrade solution to gravel bikes currently set up with 11-speed Di2.

All three series offer no new chain or cassette options, and GRX simply repurposes existing road and mountain bike cassettes. For 2x setups, the HG-800 11-34T cassette is the widest spread available, and tighter 11-30 and 11-32T cassettes are suggested, too. As for 1x options, there’s the choice of 11-40 or 11-42T cassettes from Shimano’s mountain bike series.

Shimano’s suggested cassette and gearing options.

Existing cassettes mean you can still use your old wheels. Shimano’s 11-speed road cassettes call for an 11-speed HG freehub, while Shimano’s HG-800 11-34T cassette and all 11-speed mountain cassettes will fit (almost) everything from 8 to 11-speed freehubs.

The downside to sticking with old standards is that GRX is restricted to an 11T smallest cog, meaning the maximum (suggested) range of 381% in a single ring configuration is still less than the 420% that SRAM’s 1×11 groups have long offered (when using an XD driver body).

Similar to the chain and cassettes, there are no GRX pedals at this moment. Shimano simply points to its SPD mountain bike and touring pedals (such as the ES600) as the best options.

Crank options

Sticking with Shimano’s proven road-width 24mm axles (and bottom brackets), the new GRX cranks offer a wider gearing range and better clearance than before. The chainline is pushed out by 2.5mm, giving more clearance for a front derailleur and wider tyres. This is similar to what the “Boost” concept did for mountain bikes, although there the cassette is also shifted outward by a matching 3mm – something GRX doesn’t specifically do.

The RX810 cranks are 1x and 2x-specific.

The Hollowtech RX810 crank is available in either a 1x or 2x option. The single ring version borrows Shimano’s mountain bike “Dynamic Chain Engagement” tooth profile, with the choice of either a 40 or 42T chainring.

The double version of the RX810 crank features a unique 48-31T ring setup. That’s a 17-tooth gap between the two rings, and a stark change from Shimano’s maximum chainring differential gap of 16T on the road. For comparison, pre-existing (non-Shimano) sub-compact cranks typically offer either a 48-32T, or 46-30T chainring configuration. Combining the 48-31T chainrings with the maximum recommended 11-34T cassette will provide a 479% range – massive, but still a little off the 500% that SRAM’s Eagle 1×12-speed mountain bike drivetrain offers (admittedly, Shimano will offer far tighter gaps between each cog).

Related reading: Sub-compact and gravel gearing explained.

The RX600 crank misses out on the hollow tech construction, and instead uses a forging process – gaining approximately 98g in a single-ring variant. This crank is designed for use with both 10 or 11-speed GRX setups, and will be limited to a 46-30T sub-compact option in the double ring variant, or just a 40T ring in 1x. Where the RX810 is available in three arm length (170, 172.5 and 175mm), the RX600 adds 165mm option, too.

In both cases, the double chainrings use a unique asymmetric four bolt mounting pattern similar to Shimano’s road rings, albeit smaller.

The new RX810 and RX600 cranks mount to the bike in the exact same way as existing Shimano road cranks – with bearing preload cap and two pinch bolts on the left side.

At 151mm, the width between the cranks (Q-factor) is wider than traditional road cranks, too (R8000 is 146mm). This reduces heel rub on chainstays and provides greater freedom in frame design. Previously, Shimano has offered non-series cranks with this increased width for OE bike brands to choose.

Derailleurs, and lots of them

That 2.5mm chainring offset and greater gearing jump call for a GRX-specific front derailleur. Visually, they are nearly identical to existing R7000 and R8000 derailleurs, with the toggle link construction and integrated cable tension bolt on the cable spool. There are only RX810-level front derailleurs available for 11-speed setups, with an RX400 offered for 10-speed.

With a 2.5mm chainring offset, the GRX front derailleurs are offset outboard by the same amount.

The rear derailleurs merge the function of Shimano’s new Ultegra RX clutch-equipped derailleurs with a curvy mountain bike aesthetic. All three series of derailleurs feature the same slim Shadow profile, optional Direct Mount link, and clutch mechanism as Ultegra RX, with the latter offering improved chain retention and reduced chain slap. Compared to the mountain bike derailleurs, the clutch tension is set lighter, and with lower forces in mind.

The clutch can be switched on and off, although there’s little reason to change it when riding. Our recent tests showed that Shimano’s clutch-equipped derailleurs only increase drivetrain friction when shifting.

The RX810 rear derailleur looks somewhat like a previous generation XTR Shadow Plus.

There’s a number of rear derailleur options, with RX810 offering 1x and 2x-specific derailleurs in either mechanical or Di2. A longer derailleur cage version is needed for 1x setups with 11-40 or 11-42T cassettes, while a shorter and lighter rear derailleur is suggested for 2x setups.

Shimano historically errs on the side of caution, and so while they specifically don’t recommend it, GRX could potentially be set up with wider gear ranges than stated. For example, an XT 11-46T cassette may just fit into the long-cage GRX rear derailleur, or you could potentially use that same derailleur with a 2x system and an 11-36T (not Shimano) or 11-40T cassette. However, it’s still too early to know whether these setups will work well.

Across the three series, the GRX rear derailleurs are said to work with existing road shifters. Compatibility with mechanical front derailleurs is assumed, but to be confirmed.

Overhauled shifters

Shimano’s road shifters may work with the new GRX drivetrain components, but you’ll certainly be missing one of GRX’s most notable advantages. Shimano’s research concluded that you’re more likely to descend and ride rough terrain in the hoods than the drops, and GRX’s shifters offer greatly improved braking from higher up.

As a result, all levels of GRX get an overhauled lever blade that offers a scalloped section for your finger to more naturally rest on when braking from the hoods – it’s a wonderful update compared to the slippery lump that your finger sits on with current 11-speed road shifters. Additionally, the blade is given a matte finish for better traction.

The RX810-level shifters are treated to a new textured hood cover for increased grip. Wile the RX815 (Di2) lever has the brake lever pivot point raised by 18mm in an effort to improve the braking leverage offered from the hoods. That raised brake pivot means there’s now a more pronounced nose to the hood shape, something that will likely help with grip. Despite the taller hood, Shimano has done well to keep overall bulk to a minimum.

The RX810-LA on the left (it’s has the same shape as the RX810 shifter), with the RX815 Di2 lever on the right. The latter offers a noticeably different form to existing road shifters.

And while I didn’t get my hands on it, the new Di2 shifter (RX-815) appears to be slimmer and designed with an even more pronounced hood shape, perhaps closer to what Campagnolo offers. This new Di2 shifter option also borrows Shimano’s mountain bike Servo Wave technology, allowing more immediate pad contact and amplified braking power for the same force at the lever. Servo Wave is not included on mechanical shifters.

Braking from the drops will also benefit from the increased leverage. The hex-key brake lever reach adjustment and shifting actuation is unchanged from road STI and Di2 shifters.

Shimano will also offer 1x-specific left-hand levers without the shifting internals. In the case of Di2, no such 1x-specific option will exist, with Shimano instead suggesting that the spare left-side buttons can be used for control of computers, lights, or other compatible accessories.

The textured hood is found on RX810/RX815-level levers. Lower-level levers are given a simpler hood cover without the raised tread.

Is your mountain bike in for service and you want to put a dropper post on your gravel bike? In that case, you’ll be pleased to hear GRX will even offer a left-hand lever with an integrated dropper remote when using 1x drivetrains. Available only on a RX810-level mechanical shaped lever, the RX-810-LA has a 9mm throw to operate mechanical droppers that use a cable head at the lever body. That last note may prove problematic, though, as many good droppers now put the cable head at the seatpost end.

Brakes

The disc brake calipers are a carry-over item.

With the exception of the improved lever ergonomics and the Servo Wave on the Di2 RX815 levers, the hydraulic disc brakes are carried over from the road. The dual-piston brake calipers will be offered in flat-mount only, and use the same pads as existing R7000/R8000/R9000M9100 brakes. Only RX810 and RX400-level calipers will be produced, with the RX600-level levers being matched with the cheaper caliper.

Disc rotor choice is much like choosing a cassette: pick your favourite from either Shimano’s road or mountain lineups. Where big descents are likely, Shimano still recommends the use of Ice Tech pads and rotors for more efficient cooling.

GRX can be configured with optional inline brake levers.

However, entirely new is the option for inline hydraulic brake levers. Much like the old-school inline cyclocross levers that sat on the tops of your bars, the new RX812 levers will intersect the hydraulic hose and offer optional braking from the tops of the bars. And where old inline brake levers often led to mushy and vague feeling brakes, the hydraulic nature of these should mean the only negative is weight-related.

The optional inline levers appear to mount to the bar near to the stem, and will likely require a 31.8mm round surface. And it’s quite likely that these will take the space often used for bar-mounted accessories. Both left and right version will be available, and it’s totally optional on if you want to use both, just a left, a right, or none at all.

There’s a GRX wheel set

Shimano’s new RX570 wheelset should prove to be a fuss-free choice with good value. No claimed weight has been provided, but at a guess, they’ll be over 1,800g.

Finally, there are two new aluminium wheelsets (RX570) to match the components, both sitting at a 105-level. The wheels are available in a choice of either 700c or 650b, each featuring a wider 21.6mm (19mm is standard) internal rim width and shallow 22mm rim height. They’re tubeless ready (“TL Road” fitment), and only available with a 100x12mm thru-axle front, and 142x12mm thru-axle rear.

Component weights

Weight-wise, the new GRX RX810 mechanical and RX815 Di2 components closely align with Shimano Ultegra R8020, and the final weight will greatly depend on the desired setup.

The crankset sees the most weight gain, with an RX810 48-31T crank quoted at 722g, and the 1x version at a claimed 655g. Compare this to 676g for an Ultegra R8000 50/34T.

The derailleurs are approximately on par, with an RX810 rear derailleur sitting at 251g, and an Ultegra RX mech quoted at 248g. The longer-cage mechanical and Di2 versions for 1x setups add a further 13g and 34g, respectively. Shifter and brake caliper weights have not yet been provided, but it’s expected they’ll be slightly heavier than equivalent Ultegra units.

Availability and pricing

GRX is still a couple of months away, with Shimano Australia stating that mechanical components will be available from July/August, and RX815/RX817 Di2 pieces expected nearer to September/October. Shimano USA is expecting to have components in stock a few weeks earlier.

As for pricing, RX810 components will be comparable to what Ultegra R8020/R8070 components sell for, with complete groupset prices starting from approximately AU$2,000 (US$1,400).

What’s next

In many ways, GRX provides a Shimano-approved version of what many people already run. You’re no longer forced to pick an aftermarket crank and/or chainring to get that wide gearing. And the updated hoods should provide more confident control without feeling the need to be in the drops.

It’s safe to say that GRX will be appearing on many 2020 gravel bikes, and we should be getting our hands on a test groupset soon, too.

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