The goal of this series is not to give in-depth reviews of products, but rather to highlight the few things that really matter and to solve a technical problem you may have with getting these part to do what you want.
Because let’s face it, gravel riding and racing is so individual, so dependent on where you ride, how you ride, how fast you ride and the skills you have, that the “standard setup” may not always work for you. And then you start to tinker, but you don’t want to end up with problems out in the field. So let’s start with the newest gravel groupset, Shimano GRX.
(Shimano claims “first gravel groupset”, but that’s more marketing speak and playing with the definition of words than that it reflects reality. After all, SRAM’s Force1 and subsequent groupsets are great gravel groupsets too)
A small preview of things to come appeared last year, when Shimano introduced Ultegra RX, a few gravel components that you could combine with regular Ultegra parts. But it lacked the wide range cassettes and 1x options to really be a serious alternative in this SRAM-dominated gravel market.
This year, Shimano is serious. GRX is a groupset designed from the ground up for gravel, with proper 1x and 2x options, wide range cassettes and some clever features. I won’t review each piece in detail, but pick out the things that are interesting and really matter:
The range: The new GRX range includes 1×11, 2×11 and 2×10. And within those, they also have a few different versions. This can make it confusing. In general the 10-speed bikes are sort of Tiagra level, the 11-speed bikes are more Ultegra level.
Shift/brake levers: These are awesome. Of course ergonomics are subjective, but a lot of people will love how these levers feel on the hoods. And Shimano has also changed the angle of the levers and the pivot point to make it much easier to brake from the hood position.
The mechanical shift/brake lever ergonomics on the hoods and while braking from the hoods are fantastic.
As you can see above, the mechanical and Di2 versions are different. I prefer the mechanical shape, it feels more natural in your hand. The difference over regular Shimano road shifters is remarkable; this is really a major step forward. And there is no reason to restrict this to gravel, you can put them on your dedicated road bike too if you like them.
1x gearing: TheRX-812 rear derailleur (RX-817 for Di2) is specifically for 1x and can handle up to 42T for the biggest cog. You can run Shimano 11-42 cassettes, or 11-40 for those who want a bit tighter range . You can even run a SRAM 10-42 cassette. That is not endorsed by Shimano but it works flawlessly in our lab and outside.
Combining the GRX RX-812/RX-817 rear derailleur with a SRAM 10-42 cassette? Shimano says no, I say go.
2x gearing: Quick rear derailleur basics, every derailleur has a maximum cog size it can handle AND a capacity. The capacity is the total numbers of teeth (really of chain links) it can “store” in its zig-zag shape. And for 2x, it needs be able to store both the tooth-delta of the cassette AND the delta between the front rings.
For the 1x rear derailleurs mentioned before, the capacity is 31T, which is already used up by just an 11-42 cassette. You can go a little further (which is why the 10-42T cassette also works), but it cannot handle another 16 links that you gain or lose when you shift between the front rings.
Bottomline, for 2x you need the RX-810 derailleur (RX-815 for Di2), with a larger 40T capacity (yeah!) but a smaller max cog size of 34T (boohoo!)
This means the biggest cassette you can run with this setup is 11-34. On the positive side, Shimano’s cranks come with very small inner rings (30T or 31T) so that your smallest gear can still be pretty small (30×34).
But it may come at a cost. On gravel bikes with dropped chainstays (which means pretty much every gravel bike, since they all copied the OPEN UP and 3T Exploro that pioneered it), a 30T inner ring puts the chain very close to the chainstay. So you need to be very careful in the setup to make sure that the chain length and chain tension keep the chain from swinging into it.
Another way around that is to ignore the 11-34T max cassette size Shimano recommends and install an 11-36, but whether that works or not depends on many factors in your setup, from chainstay length to chain length to alignment to chainring sizes. That said, Shimano (and also SRAM are very cautious in their recommendations, so the 11-36 cassette will work on most bikes without a problem. I just can’t guarantee it. But you can always try with the cheapest 11-36T cassette you can find.
Going beyond the Shimano gear range recommendation for 2x? Shimano says no, I say …. maybe. And I’d rather go with a bigger cassette than with smaller chainrings
The sub-brake lever: This is a nice touch, the sub-brake lever you can put close to the stem. I’d personally never use them, as I ride almost always on the hoods and not on the straight section of the bars. But if you do or are into cyclocross, this may be a selling point for you.
Mechanical vs. Di2: GRX comes in mechanical and Di2 versions. The options I described above for 1×11 and 2×11 exist in mechanical and Di2, the 1×10 is only mechanical. Di2 1×11 looks a bit silly, because there is no left brake lever without shift lever.
So you have a lame shift lever sitting on the left, unless you re-program it for a different function. Still doesn’t make it very useful, but you can program it to shift the rear derailleur with your left hand while you eat a banana with your right hand.
More problematic for me is that while for mechanical groups, 1×11 is the standard, for electronic you can get 1×12 from SRAM with a Force/Eagle combination. That’s a bit more expensive, but it’s nice to have that extra gear if you’re going to spend good money anyway.
1x mechanical GRX is great, 1x Di2 a bit pointless. For 2x, both mechanical and Di2 are nice (but of course 2x is a rapidly dwindling market for gravel).
So how about the Di2 in 2×11 setup? There the left lever obviously has a real function, and the one missing cog compared to SRAM Force 2×12 is not that big a deal (both are more gears than you need). And in 2x, Shimano actually has SRAM beat on useful range. SRAM’s smallest gear option is 33x33T if you combine their 10-33T cassette with their 46/33T crank. Shimano’s smallest gear option is 30x34T, which is more appropriate for really touch gravel sections. As mentioned before, the big caveat is if the 30T chainring will clear your frame.
I hope the above is useful for you, if you have any questions, additions or suggestions for future topics, feel free to post them below. Interested in a gravel bike with Shimano GRX, then check out this Exploro. More of a SRAM rider? Then maybe the Exploro Pro Rival and Exploro Team Force at a similar price points could be of interest. Or read my thoughts on hacking SRAM Force/Eagle AXS for gravel bikes.