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

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

Old 05-11-19, 04:45 PM
  #1  
Clyde1820
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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).
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Old 05-11-19, 05:08 PM
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In theory you could use a

Middleburn Incy 32-20 and a
Shimano 11-42

and arrive at
12.96 g.i.

There is a page on climbing gears HERE

Another idea would be to use an e-bike and only engage the motor while climbing.
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Old 05-11-19, 05:14 PM
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I think there would be a number of tools that you could use to get low gear inches.

Small Tire Bike. For example a 20", 406, or 451 BSD. Bike Friday? Brompton?

Mountain Tamer:
Mountain Tamer Chainring Adapters, Gorilla Brake Beefers, Gorilla Headlocks and more
That should get you down to about 17T

Internal Gear Hub:
SRAM Dual Drive (note, there is a lot of ambiguity on whether this will be continued to be supported, see Sturmey Archer below).
https://www.sram.com/sram/urban/products/sram-dd3-24
• Gear 1 - 73%
• Gear 2 - 100% Direct Drive
• Gear 3 - 136%

Sturmey Archer Dual Drive:
Sturmey-Archer | CS-RK3 Silver
• Gear 1 - 75% (- 25%)
• Gear 2 - 100% Direct Drive
• Gear 3 - 133% (+ 33.3%)

Really big rear cassette:
40T is now common, and 50T is also popping up. Bigger?
You likely will have to use a MTB rear derailleur, and if on a road bike, some kid of a pull converter, or using the Microshift Mega shifters.
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Old 05-11-19, 05:25 PM
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Is there a good selection of 24" tires. (Used to be a junior racing size.) A 24" bike with a 24 front ring and 42 rear would give 13.7 GI and you can use all available parts. (Might require a custom frame, but that could be fun and address any number of other issues as well.)

Ben
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Old 05-11-19, 05:32 PM
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I have an 11-42 cassette and a 24/34T crank on a drop-bar mountain bike. I think that puts the lowest gear at 16 gear-inches. It is very hard to pedal with a high enough cadence to keep from falling over in that gear, yet there is still steep stuff I have had to push the bike up.

Last edited by Cyclist0108; 05-11-19 at 05:37 PM.
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Old 05-11-19, 05:42 PM
  #6  
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9 speed Sunrace 11-40T rear cassette. 40-30-22 crank Shimano FC-M4050 2-Piece or FC-MT300, Shimano Deore rear Derailleur RD-M592 , front derailleur FD-M4000 top swing and finally an aMTBer 20T front chainring. You will need to file away some of the spider on the cranks and part of the end of the bolt heads to clear the chain. This combo works. Cross chaining on the 20-11 means a little bit of chain drag but it's still rideable, just noisy enough to remind you not to do it. My partner has done a few thousand loaded km on this combination.
Gives a ridiculous gear range of 727%
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Old 05-11-19, 06:13 PM
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Originally Posted by wgscott
I have an 11-42 cassette and a 24/34T crank on a drop-bar mountain bike. I think that puts the lowest gear at 16 gear-inches. It is very hard to pedal with a high enough cadence to keep from falling over in that gear, yet there is still steep stuff I have had to push the bike up.
Yeah, this is what stops me. My low gear is typically a 22/30 (Campagnolo just does not *do* big cassette cogs) but that is low enough for me to plug away at a bit less than three miles per hour on the steep stuff. If I were to get a lower gear, I could spin a bit faster but I still would need to keep my speed the same to keep my balance.
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Old 05-11-19, 07:07 PM
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Have you ridden a bike with gearing in the teens? I built my MTB's "K-Mart triple" drivetrain in the '80s and my 22F/34R gives me about a 17GI low. If you'll be riding upright on a slope steep enough to require that gearing you'll probably need weight over the front wheel to keep from going over backwards.
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Old 05-11-19, 07:31 PM
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700Cx32 wheel: 40T chainwheel + 21T cog + Rohloff hub = 14 g.i. low.
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Old 05-11-19, 07:41 PM
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20x1.75 wheel: Nuvinci N380 + 20T cog + FSA Patterson crank (stock 28T) = 13 g.i. low.
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Old 05-12-19, 12:45 AM
  #11  
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Originally Posted by thumpism
Have you ridden a bike with gearing in the teens?
Yes, I have. Down to about 19 g.i. Works fine. And I'm comfortable with the slow speed and cadence involved.
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Old 05-12-19, 12:48 AM
  #12  
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Originally Posted by thumpism
... 22F/34R gives me about a 17GI low. If you'll be riding upright on a slope steep enough to require that gearing you'll probably need weight over the front wheel to keep from going over backwards.
Lack of power in the leg is what requires sufficiently low gearing. It won't be a 30% slope or anything like. (So, "going over backwards" isn't a risk.)

But due to old injuries one of my legs simply can't bring sufficient power for moderate hills. And so, for me it's a question of cadence and a max amount of power ... which drives the gearing question, as short of an e-bike solution is about the only option available for my situation.
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Old 05-12-19, 03:01 AM
  #13  
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Originally Posted by thumpism
Have you ridden a bike with gearing in the teens? I built my MTB's "K-Mart triple" drivetrain in the '80s and my 22F/34R gives me about a 17GI low. If you'll be riding upright on a slope steep enough to require that gearing you'll probably need weight over the front wheel to keep from going over backwards.
Or just a heavily loaded bike and a really steep long hill. 36/19 Rohloff with 26" wheels = 14GI, sometimes I'd like lower but Rohloff says no. I can ride slower than I can walk.
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Old 05-13-19, 09:51 AM
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I'll echo what others have said, that is REALLY low. I stop most my bikes at 19, because even the one at 16.7 or so gets used so infrequently I can't justify it. At 14, you'd need a 90RPM cadence to keep 3.4mph, which is about the point I find it starting to become difficult to keep in a straight line.

To think of it another way, from 19 to 14 is 35% step, which is huge.
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Old 05-13-19, 11:14 AM
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I have been planning on setting up a trike for cargo hauling/towing. That should help me with stability for those really low speeds. And, I should be able to completely stop, put the brakes on, and rest if necessary.

I believe there comes a point where low gearing would make it easier to continue pedaling than to get off and push.
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Old 05-13-19, 12:05 PM
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mountain tamer quad *with a 16t cog.. ?

Or Schlumpf mountain drive geared crank a 2.5 reduction gear factor so 34t and '13.6t'
bolting a 27t directly to the gear case.. would act like a 10.8t in low gear..

at a certain point , super low gears are restricted by practicality to trikes..

because you fall over with insufficient forward momentum on 2 wheels on a hill ..
* my conclusion after trying the Quad on my mountain bike ..

I have a 17" low on my Brompton+ mountain drive .. 54 , '21.6' '/, 15 X 16" wheel....

'2 foot gear' is less work .. aka get off and push .. [ UK calls non motor bikes 'push bikes' ]







...
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Old 05-13-19, 12:55 PM
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I would walk the bike if I needed less then the 18 gear inches offered on a mountain bike. And the only reason they need 18 is because they may be climbing steep hills in soft gravel or on wet grass with tires sinking into the ground. On most paved roads, or even seasoned gravel roads a low of about 30 gear inches will probably be fine for most older men in average condition.

There is a reason many road and hybrid bikes often go no lower than 27 gear inches. On paved or seasoned gravel roads that's low enough to get up most hills we are likely to encounter. I can understand some needing lower gears for touring with lots of gear and for some extreme conditions, In which case a 46/30 chainring might do the trick.

Clyde 1820.

You might consider one of those electric assist bikes if a mountain bike does not go low enough and if you have the funds. There not as heavy or complex as a full electric bike and can be pedaled on flat or slight inclines without too much effort. When the need arises, The electric motor might make it easy enough for you to get up many hills.

Last edited by xroadcharlie; 05-13-19 at 04:06 PM.
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Old 05-22-19, 01:47 PM
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Originally Posted by 79pmooney
Is there a good selection of 24" tires. (Used to be a junior racing size.) A 24" bike with a 24 front ring and 42 rear would give 13.7 GI and you can use all available parts. (Might require a custom frame, but that could be fun and address any number of other issues as well.)
There's one I hadn't thought of. 24in rims. Hm. Thanks.

There are, from time to time, occasional ads for 24in Stumpjumper models. Might be an option. (I'm certainly on the shorter side of things, so it wouldn't be an intolerable setup.)
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Old 05-22-19, 02:05 PM
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Originally Posted by wgscott
I have an 11-42 cassette and a 24/34T crank on a drop-bar mountain bike. I think that puts the lowest gear at 16 gear-inches.
Yeah, the newer 10spd and 11spd setups have the ability to get the larger cassette cogs while still having sufficiently small chainrings.

One crankset maker, out there, is B.O.R. (Germany). They've got a 2x crank that supports down to 20T chainrings, such as on a 34/20T 10spd. With a long-cage (SGS?) derailleur and 11-42T cassette, on a 26x2in tires, that'd be ~12.5 gear-inches low, ~80 gear-inches high.

Options to consider.
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Old 05-22-19, 02:08 PM
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Originally Posted by Trevtassie
Or just a heavily loaded bike and a really steep long hill. 36/19 Rohloff with 26" wheels = 14GI, sometimes I'd like lower but Rohloff says no. I can ride slower than I can walk.
A Co-Motion Pangea 26in Rohloff 36/19. That'd work.

Hadn't been considering the Rohloff, but I'll look into it.



Thanks everyone, so far. Very helpful.
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Old 05-22-19, 03:51 PM
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My Co-Motion Pangea Rohloff has a 50 to a 20 tooth belt drive on it. I am heavy and pushed up a very steep hill in 1st gear yesterday. I was running around 3.5mph with a head wind. I stopped several times to catch my breath. Depending on what gear calculator I use, low gear is either a 17" or an 18". High gear is either a 92" or a 95" gear. The low gear on a 36/19 would be a 13" gear. The high gear would be a 70" gear. If you want the widest gear range with plenty of low and high on a 26" and up diameter wheel then I would use a Schlumpf Mountian Drive.
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Old 05-22-19, 04:58 PM
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Originally Posted by Clyde1820
A Co-Motion Pangea 26in Rohloff 36/19. That'd work.

Hadn't been considering the Rohloff, but I'll look into it.



Thanks everyone, so far. Very helpful.
I wouldn't Rohloff I had my time again. Better off going a Sunrace 11-40 cassette in 9 speed and a 20-30-40 front. More gear range than a Rohloff, about 1000 bucks cheaper and lighter too. You could carry a spare derailleur, chain and cassette and still be lighter.
Even heavier in my case because the restricted gear range of the Rohloff meant I stuck an ATS speed drive on... with the super low gearing you run out of gears with a tail wind or on slight downhills otherwise.
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Old 05-22-19, 06:06 PM
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22t chainring, 42t cassette, and 26" tires gets you under 14 gear inches. This can be accomplished with non-exotic parts. You can do this with a 9, 10, or 11 speed setup, double or triple crankset.

In the small cog / small chainring the chain might be loose and floppy, in which case avoid that gear selection.
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Old 05-22-19, 08:33 PM
  #24  
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Even a 7 speed (sort of).

On one bike I took a 26" 7 speed rear wheel and changed the cassette body to accept an 8 speed Sunrace 11-42 cassette. On another bike I swapped out a Shimano triple for a Sram 42/32/22 crankset.

Put both parts together and you have that 22 -42 granny.

As it is the 42/32/22 triple with an 11/36 cassette is very low geared. I can climb steep stuff to the point that the front end comes off the ground and I can't steer any more.
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Old 05-22-19, 10:22 PM
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I had a Sturmey Archer CS-RK3 hub, which takes a slot-on cassette.

My largest cog on the back was only 34T and the smallest on the front only 28T but in 1st on the hub that gear was stepped back 133%. You could of course use 50T rear and 22T front with that, and tow a truck if you could get it to move without falling off.
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