Eric F 

Recent gravel rides have made it clear to me that I could make use of a little more at the low end of the range, and the top end of my current setup is unused.

Current: 50/34 x 11-36 (11s)
The overlap between rings effectively gives me 15 unique ratios, with the top 2 essentially inconsequential.

New: 38T x 11x42 (11s)
38x42 will be the lower ratio I’m feeling like I need, and the 38x11 will get me above 25mph at a comfortable cadence. The steps in between are spread out a bit more than the 2x setup, but not much, and I think it will be good for my needs. I had initially thought of going with a 36T ring, but I think it will sacrifice too much on the top end to make me happy.

The new setup will be an XT cassette, XT M8000 long cage derailleur, with a Wolf Tooth Tanpan to adapt with my existing Ultegra levers.

As much as anything, this is an experiment to see if the 1x hype for gravel bikes is real (I like it a lot on my MTB). I can easily switch back to 2x, or try a different ring, if I’m not digging the new setup.

I’m intending to do some gravel events (including BWR San Diego), but I’m not racing for placing, so ultimate speed is not a top priority. The lower low-end range will hopefully help me just finish on a route that is way out of my comfort zone.

SoSmellyAir

Why not just use a GRX RD-RX812, which will work with a 11-42 cassette?

SHIMANO GRX Rear Derailleur 11-speed (42T max low sprocket) | SHIMANO BIKE-EU

The GRX RD is $120. Wolf Tooth Tanpan is $45. XT RD-M8000 is $65. $45 + $65 = $110, so cost-wise it is a wash.

Fentuz

I would consider a SLX 11-46 cassette too

msu2001la

I'll be interested to hear what you think.

I love 1x, mostly because of the clutched RD and narrow/wide rings which eliminate chain slap and keep everything secure when bouncing around on rough terrain. I'd second the GRX 812 rear derailleur for this application, as it seems better suited for road shifters and should be able to handle the range you're looking at. Being able to switch the clutch on/off is an added bonus (though I mostly just leave it "on" all the time now).

I run 40T (rough gravel/CX) and 44T (road and light gravel) on my 1x bikes. In both cases I run an 11-32 rear cassette so I'm on the opposite side of the range as you - it's flat here and I rarely use the lowest ratios. A 36T would probably be too small for most of the riding I do.

t2p

XTR or Garbaruk cassette might be options if you want to shed a few grams from the XT 11-42

not sure of the tooth counts though - XTR might be 11-40 (?)

XT 11-42 cassette cost is reasonable - but it’s relatively hefty 430 g or so (?)

t2p

I have one 1x bike with 44 and 10-42 cassette

only have a few short rides on it

will be swapping to 40 t chainring soon - don’t need 44-10 - and this should also reduce use of the 42t cog which is a big step (6t) and is alloy

Koyote

Given that you sometimes ride a SS, I'll predict that the larger gaps (on some range of the cassette) will give you little difficulty. Most SS and fixed riders have learned to spin at different cadences.

For gravel riding/racing, the top end is less important, since you'll likely only hit >25mph on descents...And those are great for recovery (i.e., tuck and coast) and/or are often rough enough that you wouldn't want to go too fast anyway.

Eric F 

I guess that probably would have been a good choice. My lack of familiarity with GRX had me looking at MTB options, and the XT gives me the option to run an 11-46. Does GRX play nice with MTB cassettes and road shifters?

Eric F 

I have a Garbaruk cassette on my MTB, and I like it a lot. I considered it for my gravel bike, but the only 11s options are 11-46 and 11-50, which aren't where I was wanting to go with this. I also didn't want to go that expensive.

SoSmellyAir

From the Shimano webpage I linked above:

"The RD-RX812 rear derailleur is compatible with mtb cassettes with a 42T low sprocket max."

"Compatible with current road DUAL CONTROL LEVER."

Eric F 

Good to know. Thanks. Had I bothered to research it before, I might have gone that way.

jonathanf2

Hi Eric,

I would most definitely go with the GRX 812 RD if you plan on running 1x, since it's compatible with your Ultegra 11 speed shifters. Another option is to stay 2x, pick up a GRX crankset, GRX 2x FD/RD and you can use your road cassettes. That would get you lower gearing while gaining higher gearing over a 38t/11-42t setup.

As for me, I'm running the 812+Goatlink with an 11-50t cassette and 40t chainring. I can easily hit 25mph + around the Rose Bowl loop with this setup and even get up to 30mph on short sprints. This also allows me to spin through those spicy climbs through Glendale Sports Complex to Cherry Canyon and get through the climbs near JPL.

Darth Lefty 

But don't you need a 20:36 low gear for ascending Stelvio with luggage and 53:11 for descending from the Rockies on the interstate?

Eric F 

The stuff I listed above has already been purchased. Maybe I'll make the change to a GRX RD in the future. I'm sticking with the Ultegra crankset because it includes a power meter that I don't want to lose or have to replace. and I'm not seeing any advantage to a GRX crankset. I can always go back to the 50/34 2x, if I need more range. The only Shimano 11s road cassette I have is the 11-32 that originally came with this bike. I've already determined that it doesn't suit my needs.

Eric F 

Not today.

Steve B.

I would simply swap the crank to a 30/46. You get a lower gear, which is desired and keep the 2X, which should be desired.

Eric F 

Swapping the crank also means replacing a power meter, which drives up the cost significantly. As I mentioned, part of this is also about trying a 1x system to see if it is something I want to stick with.

As far as overall range, a 30/46 with my current 11-36 cassette would extend the range even lower than my intended 38x42 low gear, but would still have a couple of gears on the high end that I don't seem to have much use for. Within the range of gears that I actually use, the only advantage I see in a 30/46 2x is a couple more steps in the mid-high range.

Why should a 2x be desired?

Steve B.

I prefer 2X if I am riding mostly asphalt, as there are more intermediate gears, cassette dependent. I ride on flat LongIsland and use a 12-25 cassette and mostly sit in the 46 ring all the time. Its all about how and where you ride and only you know the answer.

Eric F 

I'm making the 1x change to my gravel bike precisely because my riding is not flat very much, and have bumped against times when I was looking for something lower than 34x36. Maybe it will turn out that I don't like the 1x. If that's the case, I have lots of options.

jp911

I made a similar swap from a compact 2x to an 11-42 XT cassette-based 1x and never looked back. I have 38, 40, and now 44 chainrings, so it took some experimentation to find the "sweet spot" for me. Also, the tanpan + XT works fine, but the GRX setup is just more straightforward.

Steve B.

Lot of good reasons to go 1X, especially if in hills with a lot of constant changes. Not needing to think much about front AND rear gear moves is nice, I have 1x on 2 mt. bikes, would never go back to anything else.

Eric F 

I decided to go with the GRX 812 rear derailleur for the simple reason of keeping things simple.

I’ll stick the XT RD and Tanpan in a drawer in case I decide to go 11-46 in the future…or maybe I’ll sell them.

Fentuz

your grx 812 is specced for 11-42 so it is lkely it will work with 11-46 slx like most 11-42 derailleurs.
issues tend to happen for 11-50

SoSmellyAir

I have the GRX crank that comes with 48/31 chain rings; if they wear out I will likely switch to the cheaper 46/30 chain rings.

Simple is best.

t2p

I believe the GRX 810 31t can be swapped for a 30t from a GRX 600 crank ... not positive - have not tried it ...

but the 48t big ring on the GRX 810 is different and mounts in a different way - compared to the 46t big ring on the GRX 600 crank

the 810 48t chainring is thicker near the mounting holes and sits in a recess on the crank arm ... the 600
46t ring is thinner near the mounting hole area and (apparently) does not mount in a recessed area

it’s possible the 600 46t chainring could still bolt on to the 810 crank - ? - dunno - but the appearance alone led to an aborted mission

46t ... 44t ... big chainring options would be welcome on the 810 crank

maybe the same person at Shimano responsible for the M900 XTR chainring sizes must have come out of retirement and selected the chainrings for the GRX 810 crank