New Sheldon Brown article on gear interchangeability
11-04-05 | 09:19 AM
#26
Unique Vintage Steel
Joined: May 2005
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From: Allen, TX
Bikes: Kirk Frameworks JKS-C, Serotta Nova, Gazelle AB-Frame, Fuji Team Issue, Surly Straggler
Originally Posted by Sheldon Brown
Sheldon "Sturmey-Archer Had Indexed Shifters 100 Years Ago" Brown
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+-------------------------------------------------------------------+ | In our country we have those three unspeakably precious things: | | freedom of speech, freedom of conscience, and the prudence | | never to practice either of them. --Mark Twain | +-------------------------------------------------------------------+
How true, how very true.
11-04-05 | 11:14 AM
#27
semifreddo amartuerer
Joined: Oct 2004
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From: Northern CA
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Originally Posted by sydney
First, your undertaning is somewhat flawed or poorly understood.And that is not because it was poorly articulated on my part. There are short cage mtb RD that do shift big cogs. Also, there are old RD that shift big cogs because old freewheels with 33 and 34 cogs were fairly common, and there were even old 38 tooth freewheels... Secondly, that cage length business is the common misconception you get about long cage RDs, and it comes not just form LBS guys that should know better.... Duno how many times I have said it, but cage length is about wrap capacity, not big cog, which is in the parallelogram design. All one has to do is look at current shimano shimano road RD specs. The big cog capability is the same for both long and short cage.That's cuz the parallelograms are identical. The 27 tooth spec is conservative tho and most will shift a 30 and sometimes, depending on the application, one can get away with a 32 with them.If it was me and I wanted to use a 32 or bigger cog, I'd just go with a mtb RD, unless I had a road type just lying around and didn't mind spending some time fiddling with it. Campy spec does not tend to be as conservative and one can get away with less with them...A Shimano mtb RD is different in that in order to clear the bigger cogs involved, it tracks a steeper angle as it traverses the cassette, and that applies wether it is a long or short cage model.
Actually I think you are saying the same thing but I think you're arguing from the opposite way. I mentioned you specifically because you have indeed repeated it so many times, and it finally sunk in, through all of the layers of smoke.
Let's review. I said:
Originally Posted by 'nother
That is to say: a short-cage derailer will not generally handle a 32 or 34T cog . . . however, not necessarily because of the cage length, but because of the length of the parallelogram/arms.
However, relative to Sheldon's article, what I'm referring to is the part that says: Long-cage derailers have greater takeup capacity, and work with all types of cassettes.
Which to me is a bit misleading, based on my understanding and first-hand experience, which is: simply being "long-cage" does not mean a RD will handle any cassette (e.g. any cog size, which is what I assume Sheldon means when he says "all types of cassettes").
I do not think my understanding is flawed as you proclaim, but please feel free to correct as necessary.
11-04-05 | 11:30 AM
#29
Senior Member
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Originally Posted by 'nother
Actually I think you are saying the same thing but I think you're arguing from the opposite way. I mentioned you specifically because you have indeed repeated it so many times, and it finally sunk in, through all of the layers of smoke.
Let's review. I said:
Now, I'll grant that you can pick on the first part of this as being inaccurate, since there are indeed short-cage derailers that will handle 32+, but to evaluate the entire statement on the basis of that phrase alone is to take it out of context improperly. The bit I've emboldened above is the important part, and I don't think that's in any way contradictory to what you've said, or to reality.
However, relative to Sheldon's article, what I'm referring to is the part that says: Long-cage derailers have greater takeup capacity, and work with all types of cassettes.
Which to me is a bit misleading, based on my understanding and first-hand experience, which is: simply being "long-cage" does not mean a RD will handle any cassette (e.g. any cog size, which is what I assume Sheldon means when he says "all types of cassettes").
I do not think my understanding is flawed as you proclaim, but please feel free to correct as necessary.
Let's review. I said:
Now, I'll grant that you can pick on the first part of this as being inaccurate, since there are indeed short-cage derailers that will handle 32+, but to evaluate the entire statement on the basis of that phrase alone is to take it out of context improperly. The bit I've emboldened above is the important part, and I don't think that's in any way contradictory to what you've said, or to reality.
However, relative to Sheldon's article, what I'm referring to is the part that says: Long-cage derailers have greater takeup capacity, and work with all types of cassettes.
Which to me is a bit misleading, based on my understanding and first-hand experience, which is: simply being "long-cage" does not mean a RD will handle any cassette (e.g. any cog size, which is what I assume Sheldon means when he says "all types of cassettes").
I do not think my understanding is flawed as you proclaim, but please feel free to correct as necessary.
Last edited by sydney; 11-04-05 at 11:36 AM.
11-04-05 | 11:51 AM
#30
Senior Member
Joined: Feb 2005
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Originally Posted by Expatriate
They need the clearance for grinding, at the expensive of chain wear.
Good article BTW, but it doesn't explain why I have a hard time shifting my short cage XC Pro rear mech onto the 28 rear.
11-04-05 | 05:12 PM
#31
Senior Member
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From: Oklahoma
Bikes: Trek 5500, Colnago C-50
Originally Posted by shane45
Hey - you guys knock it off!!! I need to find out why I'm not supposed to shift from big ring to middle ring, and you guys are clouding the issue with all this other mumbo-jumbo!!! 
Sheldon's bike wisdom and advice has been a huge help to a lot of people including me, but I don't always agree with him and I don't think he expects everyone to agree with him all the time.
Al
11-04-05 | 05:16 PM
#32
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From: Oklahoma
Bikes: Trek 5500, Colnago C-50
Originally Posted by 'nother
However, relative to Sheldon's article, what I'm referring to is the part that says: Long-cage derailers have greater takeup capacity, and work with all types of cassettes.
Which to me is a bit misleading, based on my understanding and first-hand experience, which is: simply being "long-cage" does not mean a RD will handle any cassette (e.g. any cog size, which is what I assume Sheldon means when he says "all types of cassettes").
I do not think my understanding is flawed as you proclaim, but please feel free to correct as necessary.
Al
11-04-05 | 05:58 PM
#33
Read the article, all of the hulabaloo over shifting from big/small to middlle/small loses significance when you read Sheldon's statement in context. He also explains why it can be bad (see bold print).
There is a lot of confusion about the compatibility of narrow 9- and 10-speed chains with older cranksets. Shimano says you should replace the inner chainring(s) with specially designated 9- or 10-speed ones, but then they're all too eager to sell you stuff, whether you need it or not.
These chainrings have the teeth slightly farther to the right than the older chainrings to work a little better with the narrower chains. There is no difference whatever in the crank spiders.
The manufacturers also concerned about clueless users. The worst-case scenario is that you will be riding along with the bike in its highest gear (large front, small rear) and then for some bizarre reason shift down in front before downshifting in the back. (There is no shift pattern in which it is reasonable to shift in this sequence.) If you do shift this way, there's a small chance that the chain might "skate" over the edges of the teeth for maybe half a turn.
In practice this "problem" almost never materializes. Many, many cyclists are using 9- and 10-speed chains with older cranksets and having no problems whatever.
These chainrings have the teeth slightly farther to the right than the older chainrings to work a little better with the narrower chains. There is no difference whatever in the crank spiders.
The manufacturers also concerned about clueless users. The worst-case scenario is that you will be riding along with the bike in its highest gear (large front, small rear) and then for some bizarre reason shift down in front before downshifting in the back. (There is no shift pattern in which it is reasonable to shift in this sequence.) If you do shift this way, there's a small chance that the chain might "skate" over the edges of the teeth for maybe half a turn.
In practice this "problem" almost never materializes. Many, many cyclists are using 9- and 10-speed chains with older cranksets and having no problems whatever.
11-05-05 | 06:17 AM
#34
Senior Member
Joined: May 2005
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From: Albany, WA
Originally Posted by shane45
Jur, you need to go look at your bike.
There is MORE tension when I am in big-front and small-back, then when I front-shift only to middle-front and small-back (which Sheldon says is taboo). <snip some useless stuff>
There is MORE tension when I am in big-front and small-back, then when I front-shift only to middle-front and small-back (which Sheldon says is taboo). <snip some useless stuff>
11-05-05 | 08:31 AM
#36
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From: North Central Massachusetts
Bikes: Cannondale R600
Thanks to all the posters - some really good points here; hopefully I am absorbing this all...
11-06-05 | 01:25 PM
#37
Thread Starter
Gone, but not forgotten
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From: Newtonville, Massachusetts
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Originally Posted by 'nother
However, relative to Sheldon's article, what I'm referring to is the part that says: Long-cage derailers have greater takeup capacity, and work with all types of cassettes.
Which to me is a bit misleading, based on my understanding and first-hand experience, which is: simply being "long-cage" does not mean a RD will handle any cassette (e.g. any cog size, which is what I assume Sheldon means when he says "all types of cassettes").
Which to me is a bit misleading, based on my understanding and first-hand experience, which is: simply being "long-cage" does not mean a RD will handle any cassette (e.g. any cog size, which is what I assume Sheldon means when he says "all types of cassettes").
One of the things I love about publishing on the Web, as opposed to paper, is that when someone points out an error or ambiguity in something I've written, I have the opportunity to immediately correct/improve it.
That passage was, indeed, a bit of an oversimplification, and I didn't define "long" in the context. I've revised it, hope it's more clear now.
In my defense, I'll note that the focus of this article is on interchangeability among different numbers of speeds, not so much on range issues.
Sheldon "Appreciates Constructive Criticism" Brown
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+------------------------------------+ | Love truth, but pardon error. | | --Voltaire | +------------------------------------+
11-06-05 | 04:50 PM
#38
Senior Member
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Good stuff! I'm thinking about refurbishing an old Parkpre MTB I picked up real cheap. The frame is in good shape but the spokes are shot, and most of the components are lower end. My biggest question was whether a newer, 8 speed drivetrain setup would work. The section on cold setting sounds like a plan. I see a new Deore set-up in my future.
11-07-05 | 09:20 PM
#39
put our Heads Together
Joined: Jun 2003
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From: southeast pennsylvania
Bikes: a mountain bike with a cargo box on the back and aero bars on the front. an old well-worn dahon folding bike
I'm baffled that people still don't seem to understand why it might be a bad idea to run the smallest cog with the middle ring.
Sheldon does not say this because of the fact that the chain isn't straight. He doesn't say it because of any other principle that applies to derailleur bikes only.
imagine you had a derailleur-equipped bike that was designed to use only these two chainring-cog combinations:
56/14
36/9
All three gear ratios are the same. (4 revolutions of the wheel per rev of the cranks)
The 36/9 puts the largest amount of tension on the drive side (top) of the chain. The reason is that the part of the chainring pulling on the chain acts as a lever with a length (from the bottom bracket center) of roughly 3 inches. Your foot is pushing on a crankarm that's 6 inches or so, and if you put 150 pounds of force on that crankarm, you're putting about 300 pounds of force on the chain.
Contrast that with a 56-tooth chainring. (radius of 4.5 inches or something.) Put 150 pounds of force on the pedal, and you end up with about 225 pounds of force on the chain.
It's a matter of leverage. the ground "pushing" back on your wheel can transmit more force to the chain through a small cog. the crank can transfer more torque to the chain through a small chainring than through a large chainring. add up the competing forces and you get more chain wear.
Sheldon does not say this because of the fact that the chain isn't straight. He doesn't say it because of any other principle that applies to derailleur bikes only.
imagine you had a derailleur-equipped bike that was designed to use only these two chainring-cog combinations:
56/14
36/9
All three gear ratios are the same. (4 revolutions of the wheel per rev of the cranks)
The 36/9 puts the largest amount of tension on the drive side (top) of the chain. The reason is that the part of the chainring pulling on the chain acts as a lever with a length (from the bottom bracket center) of roughly 3 inches. Your foot is pushing on a crankarm that's 6 inches or so, and if you put 150 pounds of force on that crankarm, you're putting about 300 pounds of force on the chain.
Contrast that with a 56-tooth chainring. (radius of 4.5 inches or something.) Put 150 pounds of force on the pedal, and you end up with about 225 pounds of force on the chain.
It's a matter of leverage. the ground "pushing" back on your wheel can transmit more force to the chain through a small cog. the crank can transfer more torque to the chain through a small chainring than through a large chainring. add up the competing forces and you get more chain wear.
11-08-05 | 03:15 AM
#40
"Uh-uh. Respek Knuckles."
Joined: Jun 2005
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From: CA
Bikes: '06 LeMond Versailles, '04 S&M Beringer, '03 Quamen Bowls, '68 Raleigh Grand Prix (converted to fixed gear)
Originally Posted by OneTinSloth
only because most BMXers don't realise that 9 teeth in the back and 25 up front is a dumb idea for lots of reasons...cog and chain wear being one of those reasons.
