Low gearing -- best way to get sub-14 g.i.

Gearing question: Got a good way to get down to ~13-14 gear-inches on a bike?


Would like to have people's ideas on how to most-easily get a very low-geared setup on a bike. Why? Old injuries preclude my relying on fitness to get enough "oomph" on hills. Need lower gearing. Much lower. I'm considering the next bike's setup.

Let's focus on gearing options with actual product combinations out there.

• Purpose: urban commuting with moderate hills, but with tough old injuries making "moderate" severe in my case.
• Required "low" gearing: very low-geared setup, ideally down to ~13-14 gear-inches. (Yeah, I know. Low.)
• Tolerable "high" gearing: in the ~65-75 range would be plenty, if it could get me the desired low end.
• Gearing Possibilities:
  • internally-geared hub (IGH);
  • a derailleur setup;
  • a hybrid mix, such as a FSA/Metropolitan 2x planetary-gear crank and an IGH.

I have ridden some bikes with gearing as low as ~19 or so. Current bike is at 21 g.i. I can get the current bike as low as 17 g.i., but I know that's not going to be nearly short enough gearing.

For purposes of this discussion, let's assume I'm not interested in an e-bike. Though in the long run it might well turn out to be the only way. But, for now, let's explore non-e alternatives.

3x or 2x, in 10/9/8/7spd?
IGH (ie, Alfine 8/11 or planetary-gear alternative)?
Specific hub/derailleur/chainring/cog choices you'd suggest?

Referencing the Bicycle Gear Calculator (Mike Sherman's), in a 3x9 setup it'd take something like the following hypothetical combination to get down to 13 g.i.:

16-19-22-25-28-31-34-37-40 (custom 9spd cassette, if even possible)
20/30/40T chainrings (assuming small enough BCD to accommodate the 20T)
26x2.125 wheel
Gear-inches range: 13.0 low (20 F / 40 R), and 65.0 high (40 F / 16 R).