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Alpine vs. Half-Step Gearing

Old 03-22-09, 10:13 AM
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balindamood
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Alpine vs. Half-Step Gearing

Looking for different people's opinion on this. I am building up a long-distance light-touring/randoneuring bike and am considering the gearing. I am a near full-time commuter who really likes running blocks (1-tooth incraments on the rear freewheel/hub), but this is easier for commuting becasue I can sort of dial the gearing for a consistant route.

What I have is an older Sugino triple (with the long chainring bolts) with 50-44-32 (I also have 26, 28, 40, 42 and 48-tooth chainrings) and a wide-range 7-speed freewheel - so called halfstep gearing, or a Suntour (Sugino) set up as 52-38-24 with a 13-19 block; so-called alpine.

I guess I can try both this summer, but I was looking for what people think and where to start.

BTW-the derailuer capacity is 34T (old Cyclone GT), so the above combinations should work.
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Old 03-22-09, 05:46 PM
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Halfstep gearing generally is 3, 4 or 5 teeth between chainrings, splitting the difference between adjacent freewheel gears. 6 teeth between chainring sizes seems a bit lopsided.
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Old 03-22-09, 05:55 PM
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6 teeth between chainring sizes seems a bit lopsided
I have 40, 42, 44, 46, 48, 50, and 52T chainrings. 46-52 is what is on it.
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Old 03-22-09, 05:57 PM
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The key to half step is that the fractional difference between the chainrings (50/44 = 1.136 for you) should be half that of the freewheel cogs (so the ratio of all adjacent pairs of cogs should be 1.273). If the key ratios are as large as in your case you'll exceed the tooth-handling limits of available derailleur sets, as you try to scale to more gears. Set it up in Excel, you'll see. 50/44 is pretty darn wide. Old ones with 5 cogs usually were a 3, 4, or 5, in the front for this reason.
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Old 03-24-09, 08:15 AM
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I guess I can try both this summer, but I was looking for what people think and where to start.
You start with a review of your bicycling requirements.

In regard to "gearing" a bicycle properly, two general philosophies are practiced.

One approach answers the need for the bicycle gearing to operate well for a strong rider with an average or better power-to-weight ratio. This philosophy assume the rider needs the wide-range gearing to occasionally climb extremely steep grades.

The second philosophy considers that the rider is operating the bicycle with a poor power-to-weight ratio, and will be calling on lower gearing on many average grades. This can be the result of the rider being over weight, or the bicycle being heavily loaded with touring gear.

In the first case, the focus of gear-set and chain-set is keeping the all gear rings normal size and adding an additional "granny sprocket" to the chain set to be used sparingly in rare, ultra-steep grade situations.

The second case, assumes the rider needs low gearing often due total loaded bicycle/rider weight. In this situation there is no "granny" sprocket, but instead a 32t or larger inner-sprocket, mated to larger cogs all around for the rear gears. In this case, easier shifting to the inner sprocket is achieved, and center sprocket use is increased by selecting larger inner cogs (large 26t and up) from the hub.

In other words, good gearing is a function of overall bicycle load, or route/grade requirements, not mathematical "gear step" bull****.

But I digress.
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Old 03-24-09, 09:01 AM
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Half step plus granny was commonly used when rear wheels had only 5 cogs. With a 7 speed or larger rear freewheel or cassette, half step plus granny really is obsolete as it requires a lot of double shifts moving up or down to the next closest gear.
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Old 03-24-09, 08:27 PM
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Well, it requires the same proportion of double shifts for a 5-cog as for a 7-cog.

I think we really just need to look at what happens to the half-step portion of the system. As you go to more cogs the percentage difference wants to get smaller to fit more cogs into the range that derailleurs can handle, and due to the whole number counting of teeth, it's harder to maintain the step ratio uniform across the whole cogset. The even gear spread can become corrupted.

Plus the 2XN system depends on big-big and little-little operation, which is more stressful on part with wider systems, and in any case riders today don't like to do it.

The chain angle issue just gets worse in big-big with a triple (3xN) up front, and perhaps a 7 in the rear.
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Old 03-26-09, 01:11 AM
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I used to have half-step + granny gearing on some touring bikes back in the day. I really liked it -- you could use the rear derailleur to make "full shifts," and then to fine-tune the gear you wanted you could make "half-step" shifts on the chainrings. Because the chainrings are so close together in size it made shifting the front derailleur really smooth and easy. Though you had some double shifts, with both the front and rear derailleurs shifting so easily it made sense.

However, with a modern 9- or 10-cog cassette, they don't make as much sense.
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Old 03-26-09, 07:40 AM
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However, with a modern 9- or 10-cog cassette, they don't make as much sense.
Designing a gear ratio set around gear ratio spacing has never made any sense.

Designing gearing around intended user/bicycle load has always made sense.
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Old 03-26-09, 07:47 AM
  #10  
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Yeah, i figure most people can't understand most of my posts - here's the simple answer.

For a normal rider, needing to climb a remarkable grade, you design a normal system with a granny gear.

That's two big rings and a inner granny ring .

For a fat guy or a loaded touring bike, you design a system with "two granny gear rings" and one big "overdrive ring" when going downhill or fast.

One system is used pretty normally - the other system uses the two inner chain wheels all the time.
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Old 03-26-09, 07:49 AM
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Originally Posted by Richard Cranium View Post
Designing a gear ratio set around gear ratio spacing has never made any sense.
I don't think I understand your point.

Say I have an intended use in mind and I've decided I want a gear range from around 20 to 25 gear inches on the low end and 100 gear inches on the high end. I have a number of ways to accomplish that. Especially if I have an older bike, and I'm considering whether to upgrade the drivetrain, or I have a preference for doubles vs. triples, or prefer downtube shifters vs. brifters.

Why wouldn't I want to understand the math involved in the gear ratios I'm using - and whether I have lots of double shifts, or whether I have lots of overlapping gears, etc.?
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Old 03-26-09, 10:04 AM
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Originally Posted by BengeBoy View Post
I don't think I understand your point.
Although I usually disagree with and ignore Cranium....

I think his point is that you should focus more on overall gearing range than on gearing gaps. Since you plan to tour on this bike, I'd say you need to go pretty low; 20" is about right. I don't think he understands that the OP is focusing on gearing gaps and therefore cadence.


Originally Posted by BengeBoy
Why wouldn't I want to understand the math involved in the gear ratios I'm using - and whether I have lots of double shifts, or whether I have lots of overlapping gears, etc.?
The only problem I see here is that you can overthink the problem; concern about overlapping gears may actually be counter-productive. You don't necessarily want to shift all over the place just to get a more granular gear change, if that results in excessive shifting, cross-chaining, or extra stress on the chain.

So that being said....

A 7-speed system with a gearing range of 20" - 100" is going to require some pretty big gaps. You're probably looking at, for example, a 48-38-26 + a 12-32 cassette: 12-14-16-18-21-26-32.

At the risk of stating the obvious , if you really want granular gearing, you should consider a 9- or 10-speed system. In comparison to the 7 speed, a 10-speed cassette is 11-13-15-17-19-21-23-25-28-32.

In theory you could also look into a NuVinci hub, which is a "continuously variable" hub. Rather than discrete gears, the hub uses tilting balls, and thus provides completely smooth gearing ratio changes. The shifter works like a dial, i.e. instead of "2nd gear, 3rd gear" it's just a line.



In practice it's expensive, heavy, not quite as efficient as a derailleur, and might not work with your frame. 10 speed will be a better option for touring and LD, whereas the NuVinci might be acceptable for commuting.
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Old 03-26-09, 10:32 AM
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Why wouldn't I want to understand the math involved in the gear ratios I'm using - and whether I have lots of double shifts, or whether I have lots of overlapping gears, etc.?
Because you are not a "motor" nor an engine. You are a human operating a bicycle.

The overall load, or the "occasional" steep grade, are the only two scenarios I deem worth consideration for triple chain set gear systems. And these answers are based upon on what I understand actually happens to a cyclist, riding in these two situations.

This understanding has been arrived at after 40 years of cycling in both types of scenarios. Of course, there's little reason for anyone else to learn these things from me. By all means, let silly cyclists study stupid shifting patterns that are useless in real-life. Carry on.....
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Old 03-26-09, 11:18 AM
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Ok, Richard, as someone who IS willing to learn something from someone with 40 years experience, please explain your thought process in deciding how you will implement a gear train for yourself or someone else? Assume I will ride 100+ mile days with bike+rider+kit+luggage ~220#, and that I have determined the need (based on oh so human preference) for a gear range from 35 inches to 100 inches. I haven't bought derailleurs or a chainset, nor have I chosen the rear wheel design constraints. Please explain your tradeoffs, so we can learn. I am interested.

The terrain is continuously rolling mid-Michigan hills, with many climbs of 150 feet at a 5% grade.

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Old 03-26-09, 01:45 PM
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Originally Posted by Richard Cranium View Post
Yeah, i figure most people can't understand most of my posts
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Old 03-28-09, 09:40 AM
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Ok, Richard, as someone who IS willing to learn something from someone with 40 years experience, please explain your thought process in deciding how you will implement a gear train for yourself or someone else? Assume I will ride 100+ mile days with bike+rider+kit+luggage ~220#, and that I have determined the need (based on oh so human preference) for a gear range from 35 inches to 100 inches. I haven't bought derailleurs or a chainset, nor have I chosen the rear wheel design constraints. Please explain your tradeoffs, so we can learn. I am interested.
Hey, I don't want kill any gear head's buzz.

But the truth of the matter is that bicycling with a normal load requires - you guessed it - "normal gearing." A granny gear can be added to a "normal chain set." 53/39/28

Loaded bicycle touring requires a "low-gear chain set" with an "over drive" gear added for downhills and tailwinds. 53/36/28

The gear cluster selection is used to decide the overall gear-ratio range. Generally, normal riding would require nothing larger than a 26, but for loaded cycling a 32 or 34 could be used. What's important is that the space between the center and inner sprockets provide multiple ratios during climbing.

As it was previously noted, with 8spd and up clusters these days, gear "stepping" is no longer important for gear clusters, but remains of some importance for chain sets. No calculators are required, just a small center sprocket.

Last edited by Richard Cranium; 03-28-09 at 10:24 AM.
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Old 03-30-09, 12:41 PM
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Over on the touring section there was a recent thread about using wide doubles. If your 7 sp freewheel is something like a 13-32, then a 44-26 front combo will give 91" to 22". You'll be able to climb most anything and have a speed of 22mph at 80 rpm in 44/13. You'll spin out on some downhills, but for long distance it seems like a reasonable gear range. If you need more top end just do 48-30
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Old 10-08-09, 09:46 AM
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OK so in basic terms regardless of the freewheel (cassette) a halfstep is a difference of 3-5 teeth on the chainrings. so a step is a more standard difference of 9,10, 12 (52/42, 52/39, 53/39) teeth?
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Old 10-08-09, 10:43 AM
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My recommendation to the OP would include upgrading to a 9 speed drivetrain and use the Alpine crankset. As Richard stated, the rider would use the 38t chain-ring most of the time, and use the larger chain-ring for descending and the smaller chain-ring for truly steep climbs.

If the 52/38/24 crankset was combines with a 13-25 9 speed cassette, the OP could maintain 10 to 23 mph on the middle chain-ring while spinning at a 90 to 100 rpm cadence. The 13-25 cassette provides 13-14-15-16-17-19-21-23-25 cogs and should provide close gearing and a wide range without frequent changes of the chain-rings.
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Old 10-08-09, 10:47 AM
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I've found a 45-28 with a 13-26 freewheel is perfect for long easy rides for me. I use an old 86 BCD stronglight crank.

I can stay in the 45 90% of the time but when it gets steep, the 28 is a great low gear.
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Old 10-08-09, 11:42 AM
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OH just what is an Alpine? ( and I don't mean the car by Sunbeam)
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Old 10-08-09, 12:49 PM
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Originally Posted by Bianchigirll View Post
OK so in basic terms regardless of the freewheel (cassette) a halfstep is a difference of 3-5 teeth on the chainrings. so a step is a more standard difference of 9,10, 12 (52/42, 52/39, 53/39) teeth?
I don't think you can look at half-step without looking at the freewheel. IMO, half-step means half the average freewheel step (or at least close to it). So an 11,13,15,18,22,26,34 7-speed freewheel has steps ranging from ~15% to ~22% (ignoring the last 26-to-34 bailout step of 31%) with an average of ~19%. So a chainring difference of about 9 or 10% will "half-step" this cassette - 48x44 or 50x45.
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Old 10-08-09, 04:47 PM
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OY! I need another Cosmo *giggle* I am almost sorry I looked into this.
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Old 05-02-12, 04:17 PM
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The right half-step Stuff for repair and pseudo restoration

I have two serious half-step + granny bikes from the mid 1980's

a 7 speed (13-32) TREK 720 with a 48-44-24

and a Raleigh Alyeska 6 speed (14-32) running a Shimano 105 crank (triple 48-38-24) --(Not half-step yet as I need a 45 for the 38 -- this bike came as a half-step)

In looking at new stuff for restoring touring bikes from the 1980s I noticed that Salsa makes some fine chainwheels in the 130 size for Shimano 105 cranksets.

https://www.universalcycles.com/shopp...5&category=402

The 48-45 Salsa rings and then your choice of 74mm granny gear will produce some great half-step combos.

Here are the IRD freewheel cogsets available =>

https://www.interlocracing.com/freewheelbreakdown.html

There certainly are enough options available to compete with the current rage for 2x10 systems.

For me at age 65 gears above 100 are useless ...

A 48-45-24 with 6 speed 13-24
produces a really nice combination from 27 to 100 gear inches.

6 speed
13 99.7 93.5 49.8
15 86.4 81.0 43.2
17 76.2 71.5 38.1
19 68.2 63.9 34.1
21 61.7 57.9 30.9
24 54.0 50.6 27.0

27-31-34-38-43 <= granny

50-58-62-64-68-71-76-81-86-93-100 <=half-step

--- Current front derailleurs may be a half-step problem (the inner plate is way to low on most to be able to set the outer plate correctly).
My TREK is currently running an older Ultegra (it is perfect)
The Raleigh still has its Suntour AR (not as good as the Ultegra but OK as it works.)
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Old 05-02-12, 08:27 PM
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My mid-60s Legnano was a wonderful frame, fork, and wheelset, but the half-step gearing was a PITA. It's so much easier now. One can grab about the right range in front and then run the cassette. I like a big range in front and a smaller range in back. Gets the ratios closer together. I don't mind having to shift the front a little more often, since modern FDs and rings are so good. That's just my preference. Practically, I've been told that one is limited in front by the 13 tooth rule, so 52-39-26 is about it. In practice, that seems to be true. So you can have a 10 speed straight block, or almost, in back and still climb passes fairly easily, as long as your inner ring is sized for you. I think you start with Cranium's idea and fine tune it with a spreadsheet. My tandem's cruising gearing is much better with a 12-34 than an 11-34, which one can easily see with a spreadsheet, but is not obvious just looking at the parts. We don't run close ratio in the back on the tandem.
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