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Question about cog sizes

Old 10-03-12, 07:45 AM
  #1  
MEversbergII
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Question about cog sizes

Hello!

I have a question about cog sizes. I under stand that smaller cog to wheel size means a harder go. Larger is easier.

Is there a particular name for cog sets that have a sudden increase in size between 2nd and 1st cogs? That is, 2nd - x are proportional, but cog 1 is much larger. When setting up a derailer, are there special considerations for these? I understand the reasons for their use, but I'm always looking for more information.

Probably will come up with more, but until then.

Thanks!

M.
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Old 10-03-12, 08:01 AM
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I assume you mean the second cog is significantly larger than the smallest.

Cog sets (freewheels or cassettes) can be "close ratio" where the jump between tooth number is small, typically one tooth at the small end, say 12,13,14,15..... The ultimate close ratio cog set is the "corncob" where the cogs are all one tooth apart

Cogs sets can also be "wide ratio" where the gaps are larger, say 12, 14, 17,......

A close ratio cog set allows fine steps when you shift but limits the overall spread so the largest cog isn't that big A wide ratio cog set gives larger jumps between adjacent cogs but can span a wider overall range.

Last edited by HillRider; 10-03-12 at 08:08 AM.
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Old 10-03-12, 08:06 AM
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Megarange cassette.
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Old 10-03-12, 08:10 AM
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Originally Posted by bud16415 View Post
Megarange cassette.
Yeah, that's the answer. The OP's question seem to ask about the small end of the cassette but his use of "1 & 2" must have meant the biggest cogs.
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Old 10-03-12, 09:07 AM
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Originally Posted by HillRider View Post
I assume you mean the second cog is significantly larger than the smallest.

Cog sets (freewheels or cassettes) can be "close ratio" where the jump between tooth number is small, typically one tooth at the small end, say 12,13,14,15..... The ultimate close ratio cog set is the "corncob" where the cogs are all one tooth apart

Cogs sets can also be "wide ratio" where the gaps are larger, say 12, 14, 17,......

A close ratio cog set allows fine steps when you shift but limits the overall spread so the largest cog isn't that big A wide ratio cog set gives larger jumps between adjacent cogs but can span a wider overall range.
Sort of; what I meant to say is that the lowest gear (gear 1) has a cog that was significantly larger than the next cog (gear 2). The rest look to be within one tooth.

I'll look into megarange casette. Is this a common question?

M.
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Old 10-03-12, 09:23 AM
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Originally Posted by HillRider View Post
Yeah, that's the answer. The OP's question seem to ask about the small end of the cassette but his use of "1 & 2" must have meant the biggest cogs.
Kind of a lucky guess. I think of the smallest cog as “one” also but my niece is always saying things like should I be on three in the front and one in the back going by what it says on her twist shifters and I never know what she is talking about.
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Old 10-03-12, 09:27 AM
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IF the 1 tooth difference is where the 1st cog is the littlest one, like a 12 to a 13,
but, NB: 1 additional tooth is a much larger % difference
than 2 teeth going from 28 to 30.

cars start in 1st, so now the bike mech labels seem to follow
the dominant car culture.

back in the day we knew the tooth counts of the gears
and called them as such..
like 'in the 42- 16'.. [2.625:1 btw]

in order to be crystal clear .. count teeth, say the numbers.

Last edited by fietsbob; 10-04-12 at 10:35 AM.
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Old 10-03-12, 09:27 AM
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Originally Posted by MEversbergII View Post
Sort of; what I meant to say is that the lowest gear (gear 1) has a cog that was significantly larger than the next cog (gear 2). The rest look to be within one tooth.

I'll look into megarange casette.
You must be counting from the spokes and out. Most would consider the smallest sprocket, closest to the end of the axle, farthest from the spokes, to be the no 1 sprocket.

The innermost sprocket being significantly bigger is a megarange cassette, a fairly clever compromise between overall range, and close ratios. You get one bail out gear, and nice, rider friendly ratios for the most of your riding.
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Old 10-03-12, 09:40 AM
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Interesting that the small, outermost is "gear one", given most shifters I've seen make that the highest number (seven in my case). I'll have to remember that so I'm on the same page.But yeah, basically the absolute largest gear that is closest to the spokes has a larger difference between itself and it's neighbor than the neighbor and the next one down. Megarange casette.I figured it was to allow a single very open gear for certain situations. Since learning about cross chaining I haven't really used it, however.Are there any special considerations for setting up derailers so that it'll "jump" significantly further than it does between the other gears?Thanks!M.
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Old 10-03-12, 09:46 AM
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That very large cog can be used with the smaller (or smaller and smallest if you have three) chainrings with no problem. It should not be used with the largest chainring to avoid cross chaning.
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Old 10-03-12, 10:12 AM
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I do have three, though as of late I mainly use chainring 2 and alter the rear from there - hoping I'll see improvements if I only "wimp out" on hills half way. Was under the impression the largest cog was a bit too diagonal as a result but it may have been illusion / inexperience with the subject.Is the term "Alpine Gear" generally accepted? My googling took me to a page that used this term for this kind of gear, though it was apparently misused at one point to refer to 2x5 bikes. In other communities I belong to, once a term has a history of misuse, any use becomes misuse.Thanks,M.
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Old 10-03-12, 03:00 PM
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The middle chainring of a triple crank can be used with any of the rear cogs without cross chain problems.
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Old 10-04-12, 02:51 AM
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Originally Posted by MEversbergII View Post
Interesting that the small, outermost is "gear one", given most shifters I've seen make that the highest number (seven in my case).
Dunno if I can speak for the community at large, but I'd say that the reference changes depending if you're talking about the function(=which gear ratio you're in) or the item(=which sprocket you're using). Which gear you're in is only interesting when riding, and which sprocket you're using is only interesting when diagnosing a mechanical issue. Since you can't work on the sprocket while using it, there's not much of a problem.
Gear one can well be sprocket 7(or whatever your highest number are) and gear 7 being sprocket one.

Last edited by dabac; 10-04-12 at 02:56 AM.
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Old 10-04-12, 12:41 PM
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[Partial QUOTE=HillRider;14801666]I assume you mean the second cog is significantly larger than the smallest.
Cog sets (freewheels or cassettes) can be "close ratio"
Cogs sets can also be "wide ratio" whereA close ratio range.[/QUOTE]

Adding that it is not unusual to see touring cogsets where the steps are somewhere between close and wide ratio and includes one big mother of a cog that is really a granny gear for those steep hills. Examples might be a 12-34 or a 14-36 cogset. Some even have the word MEGA on the exposed edge of the biggest gear. Most modern touring RD's can handle such cogsets fairly well. For my use, I put one of those pie-pan spoke protectors behind the cogset to protect the wheel from damage.
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Old 10-04-12, 12:48 PM
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The middle chainring of a triple crank can be used with any of the rear cogs
without cross chain problems.
just that the ones on the edges, 1st and Last, are in the ratio overlap range.
so consider what your next gear may need be,
you may consider the double shift to the other chain ring , and a similar ratio,
on the rear wheel. at the point of shifting.

It is a Terrain reading .. and the bike as a tool to get you over that hill
and down the other side.
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Old 10-04-12, 12:51 PM
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I thought the OP was very clearly referring to the difference in size between the largest cog and the second largest cog on a Megarange freewheel. I also think it is fine if we refer to being in gear 1 (largest cog) based on where the corresponding shifter is engaged, especially when we are talking about shifters that have numbers printed on them (like many grip-shifters and trigger shifters).
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Old 10-04-12, 02:12 PM
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Without this vital piece of info

Originally Posted by ARider2 View Post
talking about shifters that have numbers printed on them (like many grip-shifters and trigger shifters)
it is not clear at all which end of the cassette/freewheel a person is starting from, and that's why we tend to discourage people from trying to number them. When cassettes/freewheels are listed using the sizes (say, 12-25 or 14-28) we start with the smallest, so that's how most of us think.
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Old 10-04-12, 08:22 PM
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Originally Posted by ARider2 View Post
I thought the OP was very clearly referring to the difference in size between the largest cog and the second largest cog on a Megarange freewheel. I also think it is fine if we refer to being in gear 1 (largest cog) based on where the corresponding shifter is engaged, especially when we are talking about shifters that have numbers printed on them (like many grip-shifters and trigger shifters).
+1
I thought it was clear enough what he meant by gear 1. On numbered shifters the largest cog is always "1".
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Old 10-04-12, 08:24 PM
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Originally Posted by dabac View Post
Dunno if I can speak for the community at large, but I'd say that the reference changes depending if you're talking about the function(=which gear ratio you're in) or the item(=which sprocket you're using). Which gear you're in is only interesting when riding, and which sprocket you're using is only interesting when diagnosing a mechanical issue. Since you can't work on the sprocket while using it, there's not much of a problem.
Gear one can well be sprocket 7(or whatever your highest number are) and gear 7 being sprocket one.
Very well said!
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