How to achieve the low gearing I want.

[70Herald]

Background: 1. I ride 99% in mountainous areas so always up hill with steep roads. 2. I crashed 2 years ago breaking my femur which has affected ability to really crank out strength in my left leg.  (I came into a roundabout at 28km/hr. gave a good pedal and next thing I remember is watching the asphalt skid by about 1 helmet thickness from my face- 1 broken leg, 1 badly broken helmet. Stupidly enough first thing i did was painfully get up and see if I had ripped my bib shorts  ) and then sort of walked to the sidewalk still thinking I would catch my breath and ride home but reality was a very painful ride to ER and orthopedic surgery but the bib shorts survived)

So my current set up is 2x11 105 with compact 50/34 and 11-40 in the back. perfect for just spinning up mountains without strain on my less than perfect leg. 
Putting together a new bike and since the mountains aren't getting smaller, and the leg affects me when I really push (mostly at night/next day). I would like something with similar low ratio.

My though is: (road bike)
Mechanical 105/Ultegra 11 speed with same compact front 11-40 rear is easy to find, cheap and works well. I have looked for Ultegra Di2 11 speed and haven't found anything local for sale or at a "reasonable" price.
L-TWO erx (capable of 11 speed may work with silly large rear cassette.)
Shimano 12 speed Di2 - and very small front gear sort of like gravel gearing like goldix crank with 48/32 and 11-34 in the back.

Any thought or other ideas?

[Ludo]

Sorry to hear about you call and the consequences of it.
I don’t recall if ltwoo confirm cross compatibility or if it was another system, maybe it was all the new shimano stuff. But I remember reading about the capability of a system to pair drop bar brifter with MTB RD. That would give you 10-52 range in the back, with a 32 front you can climb up walls.

[raisinberry777]

You could go much bigger with 12 speed at the back and the 105 derailleur (in mech or Di2) - 105 is rated to 11-36 so you could probably get away with an 11-42 and whatever chainrings you want at the front. 11-42 cassettes are available from Sunshine and some others.

[bichler.bua]

You could go much bigger with 12 speed at the back and the 105 derailleur (in mech or Di2) - 105 is rated to 11-36 so you could probably get away with an 11-42 and whatever chainrings you want at the front. 11-42 cassettes are available from Sunshine and some others.

Maybe take a look at Rotor 12-speed 11-39 (expensive, though, and 4 aluminum sprockets), also available from ZTTO or Goldix on AliExpress as steel version (waiting for the shipment).
1-teeth spacing at the smaller sprockets but with low gearing, chance the 39t might work with 36t rear derailleur.

[gribs]

As I've got lots of 20%+ local climbs which I pretty much I have to climb if I want to get out of the valley I built up my Light Carbon LCR017 using 12 speed mechanical 105 with a 11-39 ZTTO cassette and a GRX600 46/30 crank set. I've also got the 105 50/34 crank set and 11-34 cassette that can be easily swapped out if I'm going for an excessively flat ride.

[glepore]

I run wheeltop 12 spd with a ztto 11-34 and 48-33 up front (Carbon ti 48 and Specialties t/a 33 on a standard 110 spider on sram cranks with powermeter). Very happy with it. So I like your Goldix idea.

[Crash217]

When I go to the mountains I slap a 36/26 MTB chainring set onto my gravel bikes Senicx crankset.  https://www.aliexpress.us/item/3256805804311535.html (zeroing mtb chainring, gxp 3bolt direct mount)

Welcome to the broken femur club.  Broke mine in 1995.  2 surgeries to repair the bone, missing about 15% of the Vastus Lateralis (outer thigh muscle), a big discrepancy of the knees orientation  and a slight length difference from the operations. (i'm naturally crow footed; Dr set knee perfectly straight, no way in hell i'm going through a surgical break to repair the issue).

My power output fluctuates between a 2% and 15% variance between the legs depending on how much i'm paying attention to really using the bum leg.

On my road/gravel bike, I'm using a Shimano 11speed 105 groupset and with an 11/40 cassette in the rear and with the 36/26 chainring I can climb steep hills essentially the same as my MTB. The 26/40 low gives me .65 ratio and my MTB gives me a .64 ratio (32/50)   (Normally I run a 46/32 front ring on my main road/gravel bike)

I've played around with my mountain setup where I live (lots of slow rolling hills), and honestly unless i'm in a big group where we are cranking along in the 20+mph range, I never have an issue with the 36t front being a limiter.  If I'm going 26mph, i'm probably at least pointed down a hill so coasting a bit isn't hurting me.

[jonathanf2]

If 99% of your riding is mountainous road terrain, I'd forgo 2x all together. I'd go 1x electronic and use anything from a 38 to 44t chainring and anything from an 10-42t-to-52t cassette. I'd also consider going with an XD/R cassette. Unless you have long stretches of flats, a 1x climbing bike with large ratio cassette is the way to go.

[Cheesecake]

I dell like SRAM is the way to go, if u want to stay in the recommend gear area, they got some pretty nice gear range

[oker_s]

If 99% of your riding is mountainous road terrain, I'd forgo 2x all together. I'd go 1x electronic and use anything from a 38 to 44t chainring and anything from an 10-42t-to-52t cassette. I'd also consider going with an XD/R cassette. Unless you have long stretches of flats, a 1x climbing bike with large ratio cassette is the way to go.

here the same on my fast gravel bike(road tires most of the year) 46-10/52 with sram xdr cassetten! works fine with shimano grx 820! now you can play around with the big chainring

[Yappie28]

Im running Rotor 46/30 chainrings in the front (typical for GRX) and 11-34 ( Shimano 105) in the back. It s running well and I can hit 40+ km/h as well as climb anything up to 25% (couldnt find anything steeper nearby).

[Tijoe]

I'm running 2X 48/32 front and 10-36 12 speed cassette with Wheeltop EDS TX shifting.    I weigh 200 lbs. I am good to go climbing up to about 10% grades.  on 15%+ grades I really begin to suffer and wish I had lower gearing.

I recommend you go to an online gearing chart and look at different possibilities. Rear tire size make a bit of difference in your rollout/effective gearing.

Your body weight also makes a HUGE difference climbing! 
 
My body is becoming old with numerous wounds from the past, and I am a lot heavier than my racing days.
Over the years, I keep having to figure out lower and lower gearing to keep me pedaling up long sustained climbs and those short super steep sections.

[jonathanf2]

I'm a big fan of the 1x ZTTO 9-46/50t cassettes on AliExpress. I can run a slightly smaller chainring up front for climbing and I have that 9t cog when I need it for downhill speed or a quick burst on the flats. It's not a cog you want to push with a heavy out of saddle sprint though.

[jeffrey]

I only started riding last couple of years with a questionable FTP and I'm not ashamed of short gears
I put on a 11-40 cassette but then I still have that 11 cog staying brand new, so I will be shortly changing the chainrings too to a 30-46

I mean, if I ever end up needing a longer gear (unlikely) I can still coast or just go slower, but I found out the 40x34 to be really nice and having something extra for those steeper sections can sometimes make the difference from keeping spinning and walking.

[blob]

I have cobbled together this:

• Shimano Deore 11-51T cassette
• Shimano GRX812 rear derailleur with a Shimano XT cage (search online, it's a known hack)
• Wolftooth Roadlink
• Shimano GRX 600 crank with Specialites TA GRX chainrings (44/28T)
• long chain
• oversized pulleys (which may or may not be helping, 12T & 15T)

For the pulleys, I actually had to file down part of one of the XT cage plates to make them fit. The whole system runs fine and handles both the big-ring/big-cog and small-ring/small-cog combinations. There is a bit of chain rubbing on the front derailleur in the hardest gear of the big-big combination, and the second-to-last hard gear with the small ring also rubs a bit. The hardest gear, however, runs fine with a slightly loose chain, so I wonder if a bigger pulley would help.