Possible Maximum Gear Ranges of Each (3?) Possible Triple-Geared Drivetrain

Question

I'm looking for the absolute maximum possible gear ranges from the known/possible triple-geared drivetrains, such as the strategy noted on TrikeTech.com. This involves pairing each of the three known dual hubs, SRAM DD3, Classified Powershift, and the Sturmey Archer CS-RK3 with a traditional front crankset and derailleur.

So yeah, we're looking at a bike with three shift levers that's hungry for steep pavement.

(Internal cranks could and should also be considered for this general question, but I'm working with a standard bottom bracket shell, so that's the initial priority of my question. And IDK if there's an internal crank that can expand the possibilities further with a standard BB shell.)

I will be doing the math myself also later on, but I'm posting this question for others, as there will be some unknowns I wont be able to consider. I want accuracy and comprehensive considerations given to how someone could go about maximizing gear range with the triple-geared strategy.

I'm not an expert here. I'm assuming a triple crank would be best in this combination, but I don't know things like whether 11 speed cassettes might give some advantage here, or if there are ultra-long derailleur cages I might not know about.

In a later question I'll ask more broadly about any other strategies that might result in even greater range.

Ultimately I'm looking for massive range so I can climb and descend extremely steep grades over exceptional distances on the same bike, on pavement.

What would be super awesome is if responders could keep their answers updated if they happen to come across something to improve their strategies.

Anyhow, I feel like this is a fun question, and someone might enjoy answering. If your answer gets selected as my solution, you may see it built onto a Montague Fit 700c folding bike. LOL, my taste is eccentric, and I have a very specific adventure style for this bike.

Answer 1

A Rohloff hub has a 528% gear range. A Schlumpf Drive crankset can have a 2.5x multiplier (or divider). That would give you, in theory, a 1320% range.

If you had a 40x16 chainring and sprocket, this would give you a low gear of 18 gear inches, and a completely ludicrous high gear of 247 with the Schlumpf step-up gear. With the step-down gear, the range would be 7.5 to 99 gear inches.

Rohloffs do have limits on how much torque you should apply to them, so in practical terms you couldn't use those super-low ratios.

There's also a practical limit on how slow you can ride.

---

Sheldon Brown wrote about his 3×3×7 OTB bike, although he didn't go into details on ratios. Today, you could set up a 3×3×9, although in either case, it would be effectively impossible to follow a logical shifting pattern. In theory, you could get a range of 8–161 gear inches with that, using a wide-range cassette, but you'd need a rear derailleur with an impossible amount of wrap capacity. This is what would be your limiting factor. A more realistic setup would give you a range of, say, 16–121 gear inches.

Answer 2

You mention "triketech" which focuses on three-wheel tricycles, so balance may be completely unimportant. In personal experience, my effective slowest speed where I can maintain balance on a climb is around 3 km/h. Any slower than that and steering/balance becomes impossible.

On my 2 wheel recumbent I have a grannie gear which is around 22 tooth, and I generally can't use it while on a climb because 15 gear-inches is a bit useless - the bike is too slow, so I can't stay upright.

This is completely different to riding on the flat, where low speeds are eminently possible. I have a folding bike with a similar 15 gear inch ratio, and that tows a loaded trailer nicely on the flat with no balance problems.

Note these quoted speeds are my empirical results, yours may vary.

---

Separately - your gearing for a downhill really doesn't matter. Once you spin out, the only thing you can do is coast and enjoy the descent. So while it is nice to have a high gear for tailwinds etc, there's no specific gear requirements for descents.