Best bang for the buck? IMHO, SRAM Red or Force 22 shifters mated with a GX10 rear MTB derailleur (both are 1:1 cable pull ratio, so work fine) with a Force front derailleur. Sunrace 11-42 cassette, and whatever 50-34 chainring 11sp setup you'd like to use. Works great, inexpensive, and ALL the gears :-)

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http://bikeblather.blogspot.com/

Toss up between the little tweaks Shimano made on GRX Di2 versus Force's 12-speed that makes jumps a little less on a 1x setup. The main issue I have with Force is cassette options -- either 10-36 (too small) or 10-50 (huge range & jumps). Kind of depends on what terrain you have and if you set up 1x or 2x.

I've ridden at 1x Ultegra D2 front with XDR RD and SRAM 10-42 cassette for years, at everything from multiple times at DK to road/light gravel races with 10k of climbing. It has worked flawlessly (so long as you occasionally charge).

That GX 10 derailleur is the bomb. Can be picked up for $60 and works great, clutch and all.

The only downside I've found for it so far is the design of the B-screw mount and the VERY narrow plate edge the screw tip presses against. If the particular setup requires that screw to be screwed in quite far, it's possible for the tip to come off that plate edge it's bearing against. If that's the case, use of something like a Wolf Tooth derailleur mount extender works quite well to compensate, since then the screw can be backed out pretty much all the way.

Other than that though, I fully agree...which is why I mentioned it :-)

edit: Also, since that derailleur is "Exact Actuation" (1:1), it not only works with the 11 speed road shifters, but all of the older 10sp SRAM road shifters as well. I'm personally using it with 10sp systems, while I have friends who use it with the 11 speed shifters. All good.

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http://bikeblather.blogspot.com/

I have GRX 2x Di2 and love it. My wife is running the mechanical version. It works flawlessly, opted for 2x just to make it a bit more versatile if I want to use it on the road.

If you are using mechanical stick with it because if you opt for electronic you won’t go back and will want to change the rest of your bikes if they aren’t. If you are just buy electric as you will probably change it to that anyway!

I bought SRAM AXS but right as I was about to install I realized my 2017 Kickr doesn't accept 12-speed. Only the 2018 and newer Kickrs will accept 12-speed. So I had to return it for GRX Di2, which I love. A PIA the ass to install and their app is all but useless. But it functions perfectly. Battery lasts forever. I have AXS on my mountain bike and have been caught out with dead battery. AXS also has four batteries.

Get GRX Di2.

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The curious task of economics is to demonstrate to men how little they really know about what they imagine they can design.

I've got GRX 600 on mine and love it. I had SRAM 1x setup on my previous gravel bike and it wasn't for me. My next one will be the 2x GRX Di2.