GRX gearing options

I think it would be great to keep track in a dedicated thread on GRX gearing options. Some things I am particularly interested in.

- Understanding 2x GRX 11-speed difference and current UltegraRX derailleur
- Real world gearing options versus recommended gearing options
- After market items built to GRX spec
- Understanding of derailleur capacities

I think an understanding of derailleur capacities could really help understand what might be a better idea to try with GRX and what not. Given that 48/31 and 46/30 are both recommended with a max. cog size
of 34 in the back it makes me think that the limit to which these cranksets work at the same level can't be equal as 46/30 is a less demanding crankset than a 48/31. Similarly I would expect 46/30 to work better with a 11-40 cassette, than a 48/31. As current UltegraRX derailleurs are already proven to work with 11-40 after some derailleur twisting (see below road.cc article), I am wondering if this UltegraRX derailleur would take the 11-40 equally well as the new GRX 11-speed small cage derailleur. I hope the derailleur is improved over the UltegraRX derailleur. And if 11-40 is never to be made as crisp with 2x, let's think after market.

https://road.cc/content/feature/246424-how-get-ultra-low-gearing-gravel-bike-adventures

If I regard 34/34=1 as a typical road bike lower gear a, 30/50=0.6 as a lowest MTB gear, then I would like to achieve a 0.8 lower gear for gravel cycling. This could be achieved with a 32/40, a 31/39 or a 30/38 lowest gear. I am hopeful for aftermarket in this case when it comes to cranksets and cassettes. I hope for a good 11/38 cassette as this will likely work very well with the small-cage GRX 2x derailleur as 11-40 has already been proven to work well with the Ultegra RX derailleur. In above article. Another option to get a lower gear is perhaps to have a smaller gap in chainrings, so you can have more spread at the back. In this sense a 44/30 chainset could work, if you are will to give up some top-speed. Another thing which I would welcome are top-quality cranksets in 46/30 which are lighter and stiffer than the GRX-600 46/30 crankset, especially in shorter crank lengths. Personally one example I would like to see are Praxis Zayante or Zayante carbon cranksets in 46/30 or 44/30 with shorter cranks, and also +2.5mm chainline to blend in with GRX perfectly. I hope they don't wait for GRX to prove itself commercially but take the bet and start today. I believe one reason Praxis didn't go below 48/32 so far is the front derailleur weren't up for it, but now they are, so let's see what they do.

Would really like to hear from people if they think these thoughts make any sense?!

I think a dedicated GRX thread would be great idea.  I started one yesterday about the GRX FD but got no takers (maybe it was just a lame question).

Crossbones wrote:I think a dedicated GRX thread would be great idea.  I started one yesterday about the GRX FD but got no takers (maybe it was just a lame question).

haha, well it also affects gearing, so hope this broader topic choice helps it stick, anything on FD also welcome here, so please expand, and any feedback on my thoughts?

Easton EC90SL w/46/30 is among the lightest carbon cranksets I've found especially in shorter lengths.  I'm running this crank with 47/32 rings and Di2 Ultegra R8050 GS (Non clutch version medium cage) with ultegra 11/34 cassette for .94 lowest gear and .89 with the SRAM 11-36. The GS rear der is said to have 34 max sprocket but I've run it with a SRAM 11-36 and had zero issues.  Flawless shifting.  

We have plenty of 7+% prolonged (1-2 mile) climbs where I ride and endless rollers some of which go above 10% on a regular basis.  If I'm in shape the 11-34 cass. 32/47 chainring combo is just about perfect.  I may purchase the 46/30 Easton rings just to have the potential to go even lower but for now I'm thrilled with this setup.  The Easton EC90SL and (EC90 aluminum version) are great options to consider.   

samongravel wrote:Easton EC90SL w/46/30 is among the lightest carbon cranksets I've found especially in shorter lengths.  I'm running this crank with 47/32 rings and Di2 Ultegra R8050 GS (Non clutch version medium cage) with ultegra 11/34 cassette for .94 lowest gear and .89 with the SRAM 11-36. The GS rear der is said to have 34 max sprocket but I've run it with a SRAM 11-36 and had zero issues.  Flawless shifting.  

We have plenty of 7+% prolonged (1-2 mile) climbs where I ride and endless rollers some of which go above 10% on a regular basis.  If I'm in shape the 11-34 cass. 32/47 chainring combo is just about perfect.  I may purchase the 46/30 Easton rings just to have the potential to go even lower but for now I'm thrilled with this setup.  The Easton EC90SL and (EC90 aluminum version) are great options to consider.   

Thanks, it looks a bit like Praxis Alba cranks, although they are market leaders in terms of stiffness. Difference is also they have 48/32 and here 46/30 is an option. Finally Alba has crank lengths down to 160, while these alloy ones only go to 170, based on this I would opt for the GRX-600 165mm 46/30 cranks every day. Comparable quality likely, but shorter crank options, and obviously fluent integration in GRX family inclusive of altered chainline. 

Actually looking at the Shimano website, I see the GRX-800 RD has a capacity of 42, while the UltegraRX has a capacity of 39, which is 3 more. The UltegraRX is already capable 11-40 at the back, so this should be even easier than for the GRX-800 RD. Not sure if you could literally say that the shifting performance of the UltegraRX with 11-34 should be the same as the shifing performance of the GRX-800 with 11-37? In the case of the 48-31 chainset this could be 11-36, but somehow it's not listed by Simano to be suitable that way in 11 speed. However in 10-speed Shimano does list the 11-36 as an option in combination with the 46-30 chainset. And this is while the rear derailleur of the 10-speed GRX only has a 41 instead of 42 capacity. The 46/30 and 11-36 combo would use (46-30)+(36-11)=16+25=41 capacity. It means this 10-speed combo maxes out the recommended combo for 100%, while a 46/30 and 11-34 combo leaves 3t in reserve. However, Shimano has no 11-speed cassettes like 11-35, 11-36 or 11-37, and hence they say 11-34 is the max. Of course it's very easy to make as little new products as possible, but if they could just make one extra 11-speed cassette, sure 11-36, 11-37 and 11-38 would all just work perfectly, and they don't, while their derailleur is capable of it without any further b-screw or roadlink adjustment, that's not very customer friendly.

I didn't realize that the GRX gearing was too high until I took a loaded bike up some climbs near Salida CO, someone had mentioned it too me and I thought "oh they are not used to altitude" but I was constantly wishing for at least one (or two) more clicks to a lower gear.  With the 48-31 crank, a 11-34 cassette and 700x43 the gear inch span is approximately 25.5 to 122.2.  I think the low end, 25.5 gear inches, is too high for me on steep/difficult terrain.  I looked at upping the rear to 11-42 but that still only got to ~20.7 gear inches.  I really wanted to get down to 18~19 gear inches for the really steep stuff with a loaded bike at altitude.  Unfortunately I think the only way is a combination of smaller chainrings and a larger cassette.  Currently I have a MTB crankset (36-26) and a 11-40 cassette with a goatlink (the 10spd MTB version) on the GRX-810 RD, the gear inches is ~18.2 to 91.6, I lost a lot of top end but I'm not sure that matters much since it was only useful for +25mph peddling.  I'm curious how others have ended up hacking their GRX drive train, front and back, to get a lower gear ratio? 

Here are a couple thoughts in response to your post.  
1. A crankset is a crankset.  Other than a bit of weight, you could not discern the difference between a $500 carbon or a $50 aluminum crankset.  So just get the set that can provide the gearing you want. 
2.  I've read from a number of people on this site that you can use the 817 1x RD with a 2x setup and the only limitation is you cannot use full syncro.  
3.  I've run 46x30 with an 11-42 mechanical without any issues other than chain length.  46x42 requires a lot of chain, like the whole 116 links.  That means you are not going to be able to wrap 30x14, 13, 12, 11 or so.  You just have to pay attention to which ring you are in.   
Now I run 40x24 with a 11-42 and it still have the same issue.  When I went to di2 I figured I could just program it to shift automatically, but then my dual-sus gravel bike had clearance issues with the FD and so I'm half di2/half-mech and still have to watch my shifting.

Here is all I can respond to. I changed my Raleigh Roker Comp out about 2 years ago from the Sram Rival 1 to the new GRX 800 48/31 crank with a 11-40 rear cassette. The shifting is smooth. The only gear it doesn't like is big first ring. It makes a somewhat grinding noise when I shift up there from the small ring which I don't stay there too long. It also make the same noise when shifting down to the big low from the top end. I have learned about what gear on the low ring is the same gear ration.

Good luck
Zman