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Folding Bikes Discuss the unique features and issues of folding bikes. Also a great place to learn what folding bike will work best for your needs.

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Old 03-23-12, 09:21 AM   #1
garethzbarker
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Figuring out gears for little wheels

my lht has just about the perfect gear range for almost any ride i do. The lows are super low but I've needed each one and I only run out of high gears if there is a crazy kind of wind behind me.

I want a folding bike to have the same gears as the lht (or as close as i can get). I'd at least like to know how lose the ranges are.What's the easiest way to calculate gear ranges like that? I know there are units but have never used them.

The bike has 26' wheels, 175mm crank 26 36 48, and a 11-34t cassette. Some one teach me how to convert that to 20' wheels and 700cc please.

It's also hard to understand internal geared hubs as well. When I looked at the alfine11 the other day it lists in percent.
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Old 03-23-12, 09:36 AM   #2
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http://www.sheldonbrown.com/harris/gears/

Plug in the numbers and have fun!

IGH page: http://sheldonbrown.com/gears/internal.html

Last edited by wandt; 03-23-12 at 09:44 AM.
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Old 03-23-12, 10:08 AM   #3
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I have the same hub, a Rohloff, in 20 " wheel bike 16t/ 53t chain ring,
and a 26" wheel 16t/38t chainring.. gearing quite similar ..

Brompton 54/15t
Schlumpf Mountain drive, drops the 3 gears in my AW3 hub, low enough
to be an additional 3 gears.. L 1,2,3, <hub,high, range shift, hub low> H 4,5,6.

these are planetary gears , so shifting can take place at any speed [even stopped]
with a slight hesitation in power input..

Last edited by fietsbob; 03-23-12 at 10:11 AM.
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Old 03-23-12, 10:58 AM   #4
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I have the same hub, a Rohloff, in 20 " wheel bike 16t/ 53t chain ring,
and a 26" wheel 16t/38t chainring.. gearing quite similar ..
I don't mean to hijack the thread, but if you don't mind me asking what type of bike do you have the Rohloff (with 20" rim) and how do you like it.

I'm debating between a Rohloff or ALfine 11 for my NWT. I'm getting sick of adjusting derailleurs and cleaning chains.
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Old 03-23-12, 10:58 AM   #5
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Here's another online gear calculator: Mike Sherman's bicycle gear calculator.
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Old 03-23-12, 11:25 AM   #6
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I have a BF Pocket Llama .. but Wandt, you cannot get away from using a chain.
because of the behind the BB pivot.
The Chain-tensioner is fitted to the derailleur tab,..

Their 349 wheel Tikit unifies the rear end to include the BB,
then the Gates Belt system can be used.

Or, due to their unique pivoting dropout , a chain without a chaintensioner..

Using the BiFri PL all winter, disc brakes, Schmidt hub, dyno lights.

[trekking bars], Have a straight split bar and Ergon GC3 grips
as a packability enhanced option.

Last edited by fietsbob; 03-23-12 at 11:29 AM.
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Old 03-23-12, 11:46 AM   #7
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I have a BF Pocket Llama .. but Wandt, you cannot get away from using a chain.
because of the behind the BB pivot.
The Chain-tensioner is fitted to the derailleur tab,..

Their 349 wheel Tikit unifies the rear end to include the BB,
then the Gates Belt system can be used.

Or, due to their unique pivoting dropout , a chain without a chaintensioner..

Using the BiFri PL all winter, disc brakes, Schmidt hub, dyno lights.

[trekking bars], Have a straight split bar and Ergon GC3 grips
as a packability enhanced option.
Thanks for the info. Not planning to ditch the chain, but just the eternal gears. I've had both a Tikit and Brompton. I like the larger 20" wheels on the NWT. I've got mine setup with dyno hub and light with a SRAM DD in the back. It works great, but I'm just looking to make it the least bit better.
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Old 03-23-12, 06:05 PM   #8
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ok so now I get gear inches now. looks like I like roughly 20-115 gear inches. I still don't get how to figure out an alfine11. it's listed as 409% the equation I used for inches is
wheel x chainlink / sprocket. How do I calculate that with an alfine? I should have studied math harder....
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Old 03-23-12, 10:07 PM   #9
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The gears page at sheldonbrown.com shows how. http://sheldonbrown.com/gears/ Just select the Shimano Alfine in the hub gear dropdown box at the bottom.

For example, for a 20" (406mm) wheel and 32mm tyre, and a 46T chainwheel paired with a 16T sprocket, the Alfine gearing goes from 28" to 114".
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Old 03-26-12, 06:20 AM   #10
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Try using a big chain, wheel ie 56 tooth
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Old 03-26-12, 10:20 AM   #11
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Alfine 11.. it's listed as 409%
that is the internal gear ratio range, high is 409% bigger than the low.
Quote:
a SRAM DD in the back
once you put a cassette on with an 11t top cog, all you got left to do is a bigger chainring,
but that raises the low, so then you add a FD and double crank.

or one of the Schlumpf Speed drive cranks, the internal gear overdrive is 1.6X..
so its like, say, a 38t-60.8t, or 42-67.2t big ring..

Last edited by fietsbob; 03-26-12 at 03:17 PM.
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Old 03-27-12, 06:49 AM   #12
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I can't fit a front derailleur on my folding bike, I have an Sram Dual Drive rear hub for more gear ranges. With my 8 speed cassette, that gives me 24 gears. If you want to have the same gearing as your LHT, you might look at the Sram Dual Drive as a way to avoid having a triple crankset with really huge chainrings. The Dual Drive is a rear hub that has three gear ranges and takes a standard Shimano or Sram cassette.
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Old 03-27-12, 10:28 AM   #13
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Originally Posted by garethzbarker View Post
my lht has just about the perfect gear range for almost any ride i do. The lows are super low but I've needed each one and I only run out of high gears if there is a crazy kind of wind behind me.

I want a folding bike to have the same gears as the lht (or as close as i can get). I'd at least like to know how lose the ranges are.What's the easiest way to calculate gear ranges like that? I know there are units but have never used them.

The bike has 26' wheels, 175mm crank 26 36 48, and a 11-34t cassette. Some one teach me how to convert that to 20' wheels and 700cc please.

It's also hard to understand internal geared hubs as well. When I looked at the alfine11 the other day it lists in percent.
Rather than try duplicating the exact gearing, have you thought about having the right set of gearing to do the right job?

With a 9 speed triple, you have 27 gears, but out of the 27, how many of them you actually use them for without crossing in between?

Having toured many years and have seen people tour with less gears than necessary, like Laura Crawford and Russ Roca with their Bromptons of Pathlesspedaled, you don't really NEED to sink in so much money to get their equivalent gearing when there are alternatives which are much lighter in weight and more efficient.

For example. My light touring folding bike has a 2x9 gearing system. I have 9 speeds dedicated for flat and downhill and 9 climbing gears and I shift using my finger or toe. My cassette cogset is custom configured individually so I have the least duplicate gears. I find that using forward momentum with a certain cadence to determine proper gearing is the best formula rather than gear inches. The problem is that, the same gear inches on my 700c road bike does not work all that well on a 20" folder. Remember that while 20" wheels are easy to spin up, they are not all that easy to maintain forward momentum in rough normal roads so using a different gearing to achieve that and maintain forward momentum easily is an accurate gauge rather than what the calculator gives you. If you follow 700c road gearing like your LHT, you might find the exact duplicate gearing ratios on the folder to be a bit a tad tall spinning at the same cadence and effort level.

Internally geared hubs are nice. I have toured with a IGH before, but I realized that all I did was carry that excess weight for thousands of miles and people who I talked to toured with their Bike Fridays now will switch to a normal derailleur system once they upgrade to the newer BFs. Unless you have no choice like with a Brompton or some Dahons and Terns that you are forced to use IGH.

Last edited by pacificcyclist; 03-27-12 at 10:34 AM.
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Old 03-27-12, 11:07 AM   #14
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Rohloff IGHub [on my BiFri, and a 26" wheel trekking bike]
they are a 7 speed hub, used twice in 2 ranges 7th to 8th
the sequencing double shifts gear and range..

my Brompton AW3 speed + Schlumpf mountain drive,
between 3rd and 4th, I have to do that.
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Old 03-27-12, 11:57 AM   #15
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Originally Posted by fietsbob View Post
Rohloff IGHub [on my BiFri, and a 26" wheel trekking bike]
they are a 7 speed hub, used twice in 2 ranges 7th to 8th
the sequencing double shifts gear and range..

my Brompton AW3 speed + Schlumpf mountain drive,
between 3rd and 4th, I have to do that.
I met a guy who inherited a touring bike from his dad. This is just a normal diamond frame bike but he's got more 53 gears available I think. He's got a SRAM 3x hub mated to a 9 speed derailleur with a triple front plus a Schlumpf type mountain drive. The bike was so bloody heavy that I was having a hard time lifting it up unloaded.

But then I suppose he said he needed it to ride over the rockies and I respect everyone's needs are different.
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