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Ruler and Chain Checker are Diverging

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Ruler and Chain Checker are Diverging

Old 03-13-23, 12:58 PM
  #26  
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I'm in the "toss at 1/16" camp as well. Doing that on my own chains has resulted in chains lasting 2500-4000 miles, but other parts such as freewheels & chainrings lasting 7500 miles or more, as they don't get the accelerated wear from a too-worn chain.

I can end up checking dozens of used chains in a single shift at Rusty Spoke, all of them grubby (we don't have the time or resources to clean every chain that comes in). The 1/16" reject value is conservative, but minimizes problems with a chain wearing out other components or any reading error from chain gunk. I'll measure the wear in inches and the pin width in mm, and look for missing/reusable links or damage/twisting (it's surprising how many chains we get where the chain is opened with a tool even though a missing link is present). I'll then bag and label the chain for reuse with brand/model, pin width & optimum number of speeds (such as "7.1 mm - 7-8 speed"), wear ("none/slight/moderate") number of links, and whether it has a "missing/reusable" link or not.

A few weeks ago, I encountered a chain that had over 1/4" wear in 12". It was separated from its original bike, but I'd hate to see the rest of that drivetrain...
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Old 03-13-23, 01:22 PM
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Originally Posted by GamblerGORD53 View Post
Measuring any distance more than 12" is just plain dumb. Slackness will make a difference.
That's why you hang things and let gravity pull the slack out for you.
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Old 03-13-23, 01:26 PM
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This is all I use, accurate and fast.

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Old 03-13-23, 02:16 PM
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Originally Posted by himespau View Post
That's why you hang things and let gravity pull the slack out for you.
Or better yet, just measure when the chain is on the bike and the derailleur spring is holding it taught.
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Old 03-13-23, 02:18 PM
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Exposing my innumeracy

How do those Rohloff numbers (mm?) match up to the Park Tool and Shimano .5% and .75% wear? And the 1/32" and 1/16" of ruler users? I've Googled conversions but I can't make any sense of it.
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Old 03-13-23, 02:20 PM
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Originally Posted by Lombard View Post
Or better yet, just measure when the chain is on the bike and the derailleur spring is holding it taught.
True. As someone who pulls his chains off every 700-1000 km to give them a fresh dip in MSW (how many hot topics can we drag into this sucker ), I always have at least 2 chains off the bike hanging on a nail, so I tend to measure then.
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Old 03-13-23, 02:40 PM
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Originally Posted by Kontact View Post
Chain checker trumps a ruler. You're attempting to avoid wearing out your sprockets, and sprockets run on the rollers the checker measures, not the pins a ruler measures.

And this is what that looks like when there is no pin stretch (ruler) but roller wear:
The rollers are not a factor in measuring chain wear. The "stretch" comes between the pins and the inner plates that act as bushings. Nice drawing though.
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Old 03-13-23, 02:42 PM
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Originally Posted by nomadmax View Post
This is all I use, accurate and fast.

It is fast and NOT accurate. Mine hangs on the wall and hasn't been used in decades. The Pedro's and the high-priced Shimano are accurate.
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Old 03-13-23, 02:59 PM
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Originally Posted by RCMoeur View Post
I'm in the "toss at 1/16" camp as well. Doing that on my own chains has resulted in chains lasting 2500-4000 miles.......
Why are your chains wearing out so fast? I have a chain that has 6000 miles and it isn't at 1/16 inch yet. Granted I'm mostly a fair weather rider....at least by choice.
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Old 03-13-23, 03:15 PM
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Originally Posted by Lombard View Post
Why are your chains wearing out so fast? I have a chain that has 6000 miles and it isn't at 1/16 inch yet. Granted I'm mostly a fair weather rider....at least by choice.
Not sure. The ones that last the longest seem to be the ones I started waxing a while ago (racer and tandem), both of which are at over 4000 miles and less than 1/32" per foot of wear. I'm moving all my chains to wax as they reach their 500-mile cleaning schedules, and we'll see how that affects wear. Although Phoenix only gets 7" of rain in an average year, our Sunday rides expect the leader to show up rain or shine, and a number of recent Sundays have coincided with those infrequent showers, so some of the chains do get some foul weather exposure. I've also installed used but not worn-out chains on my commuting bike to "use them up", and they sometimes last another 1500 - 2000 miles.

None of this discussion includes the recumbent, whose current chain is from the early 1990s, has about 8000 miles on it, no measurable wear, and may outlive us all.
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Old 03-13-23, 03:25 PM
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Originally Posted by davidad View Post
It is fast and NOT accurate. Mine hangs on the wall and hasn't been used in decades. The Pedro's and the high-priced Shimano are accurate.
Link me the Shimano version and tell me how it's better.
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Old 03-13-23, 05:07 PM
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Originally Posted by davidad View Post
The rollers are not a factor in measuring chain wear. The "stretch" comes between the pins and the inner plates that act as bushings. Nice drawing though.
The only reason to measure chain wear is to predict how much the rollers are damaging the cassette cogs.

You think stretched chains are going to break or something?
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Old 03-13-23, 05:51 PM
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Originally Posted by Kontact View Post
The only reason to measure chain wear is to predict how much the rollers are damaging the cassette cogs.
Precisely. Or rather to replace the chain before you damage the cassette cogs.
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Old 03-14-23, 04:16 PM
  #39  
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Originally Posted by Kontact View Post
The only reason to measure chain wear is to predict how much the rollers are damaging the cassette cogs.

You think stretched chains are going to break or something?
If the chain is not worn the rollers won't effect the cogs. I never said anything about a broken chain.
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Old 03-14-23, 05:20 PM
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Originally Posted by davidad View Post
If the chain is not worn the rollers won't effect the cogs. I never said anything about a broken chain.
The only thing that affects the cogs is the increase in pitch between the rollers. What makes you think chain wear somehow doesn't involve roller wear when rollers are what wear out the cogs? Rollers are part of the chain.
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Old 03-14-23, 08:38 PM
  #41  
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Originally Posted by pdlamb View Post
My normal routine is to use a chain gauge (coincidentally, the CC-3.2 @Kontact mentioned) to find out if it's time to break out the ruler. However . . .

Using a ruler isn't automatic. I'll go with a longer rule, such as a measuring tape or the Park SBC-1, so I can center the beginning (1" on the tape or the triangle on the Park) on a rivet. Measure to the center of the '12" rivet', then go back and make sure the beginning mark didn't shift. Repeat at least one more time to make sure you've got the right measure. Or you can measure to one end or the other of the rivet, if you're not sure you can eyeball the middle of a rivet accurately.

And then go measure another one or two 12" sections of chain, to see if the measurements match or are longer than you want the chain to be to stay on the bike. If there's significant divergence, go with the longer measurement IME, and replace the chain.

IIRC the Pedros tool is supposed to take roller slop out of the measurement, FWIW.

My guess is that your "ruler" moved while you looked from one end to the other. That's one free opinion that's worth everything you paid for it!
I think you've just shown why chain checkers exist and should be used by most people. To do an accurate measurement with a ruler - if the user even knows about the ruler method - means the person has to be aware of how to use a ruler, commonly starting at 1" on any ruler, not just tape measures. At least that's the way i was taught in various shop classes in Jr. High. Also the user has to be aware of the potential pitfalls as you've well described. It's actually not a trivial thing to measure from "pin to pin" - they're tiny and hands aren't necessarily steady.

You, I and probably a significant portion of bikeforums denizens know this (but not all of us knurds). The typical bike user, even racer and enthusiast, doesn't know and probably doesn't care about mechanical stuff or know this stuff. So chain checkers serve a really good purpose for almost anyone who wants to know the status of the chain.

If I've cleaned a chain (mineral spirits bath) I hang it from a little nail on the edge of a shelf in my garage to dry and go ahead and measure with a ruler. If it's on the bike, every once in a while I use the Park CC4 or Pedros Chain Checker Plus II (I have one at home and the other in my travel bag.) I'm not much of a scientist so can't really tell you how the two methods compare. But if one or the other makes me think I need a new chain, I get one.

Last edited by Camilo; 03-14-23 at 08:41 PM.
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Old 03-14-23, 11:19 PM
  #42  
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What gets me with this discussion is the same thing that I find so vexing about saddle sizing:

The current marketing is that you should select your saddle's outer width based on the width of two spots you don't sit on, and then apply that to the width of a portion of the saddle you also don't sit on.

And chain wear is important because of the affect a worn out chain has on cog pitch. What interacts with the cogs and also has pitch? The rollers. What should we measure? Something other than the rollers.


Imagine going to get some new shoes. The salesperson sits you down and takes incredibly precise measurements of your ankles (not your feet), then recommends a 43 Wide. Reasonable?
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Old 03-15-23, 12:31 AM
  #43  
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Originally Posted by Kontact View Post
And chain wear is important because of the affect a worn out chain has on cog pitch. What interacts with the cogs and also has pitch? The rollers. What should we measure? Something other than the rollers.
Your points about saddles and shoes aside, you can see why we measure the pin wear from your illustration. The pin wear allows the roller to move rearward under pressure so that it no longer fits the pitch. This allows the roller to erode the edges of the cog resulting in elongation of the cog pitch. If you allow the pin to wear too much, the roller erodes more of the cog resulting in the classic shark fin in extreme cases. The cogs, being smaller in diameter, wear faster than the larger but softer chainwheels. Small inner chainrings can wear pretty fast which is why they are usually steel rather than aluminum.
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Old 03-15-23, 05:53 AM
  #44  
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Originally Posted by Camilo View Post
You, I and probably a significant portion of bikeforums denizens know this (but not all of us knurds).
Knurds?

Originally Posted by Kontact View Post
The current marketing is that you should select your saddle's outer width based on the width of two spots you don't sit on, and then apply that to the width of a portion of the saddle you also don't sit on.
Huh?

Originally Posted by Kontact View Post
Imagine going to get some new shoes. The salesperson sits you down and takes incredibly precise measurements of your ankles (not your feet), then recommends a 43 Wide. Reasonable?
As analogies go, this is probably one of the worst I've seen.

FWIW, My last chain on this current drivetrain lasted 6000 miles. The only reason I replaced it was because it had a stiff link I couldn't work out. My current chain now has 6000 miles and has about 1/32" of "stretch". So that is 12,000 miles on my cassette and crankset. I will probably replace my current chain at 8-10K miles. Will my next chain skip on my current cassette? I don't know. But I would say 14-16K miles out of a cassette isn't worth crying over.
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Old 03-15-23, 06:37 AM
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Originally Posted by davidad View Post
It is fast and NOT accurate. Mine hangs on the wall and hasn't been used in decades. The Pedro's and the high-priced Shimano are accurate.
Originally Posted by nomadmax View Post
Link me the Shimano version and tell me how it's better.
Just what I thought, crickets.
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Old 03-15-23, 06:39 AM
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When in doubt, throw it out.
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Old 03-15-23, 08:10 AM
  #47  
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Originally Posted by cyccommute View Post
Your points about saddles and shoes aside, you can see why we measure the pin wear from your illustration. The pin wear allows the roller to move rearward under pressure so that it no longer fits the pitch. This allows the roller to erode the edges of the cog resulting in elongation of the cog pitch. If you allow the pin to wear too much, the roller erodes more of the cog resulting in the classic shark fin in extreme cases. The cogs, being smaller in diameter, wear faster than the larger but softer chainwheels. Small inner chainrings can wear pretty fast which is why they are usually steel rather than aluminum.
The illustration shows that roller wear is just as important as pin wear, so I don't follow what you're saying. Trying to measure just pin wear in absence of the other types of wear that affect chain pitch doesn't make any sense, unless you can guarantee that pin and roller wear are always in a fixed proportion to each other.
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Old 03-15-23, 08:15 AM
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Originally Posted by Lombard View Post
Knurds?



Huh?



As analogies go, this is probably one of the worst I've seen.

FWIW, My last chain on this current drivetrain lasted 6000 miles. The only reason I replaced it was because it had a stiff link I couldn't work out. My current chain now has 6000 miles and has about 1/32" of "stretch". So that is 12,000 miles on my cassette and crankset. I will probably replace my current chain at 8-10K miles. Will my next chain skip on my current cassette? I don't know. But I would say 14-16K miles out of a cassette isn't worth crying over.
Some people put so little energy through their drivetrains that discussions about chain wear, lubricants, etc seemingly don't apply to them. Congrats on your long chain life - you really must not be hammering. You're in the same class of people that go years on the same disc brake pads and object when anyone says they wear quickly - there's always someone like that on a bike forum.
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Old 03-15-23, 09:16 AM
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Originally Posted by Kontact View Post
The illustration shows that roller wear is just as important as pin wear, so I don't follow what you're saying. Trying to measure just pin wear in absence of the other types of wear that affect chain pitch doesn't make any sense, unless you can guarantee that pin and roller wear are always in a fixed proportion to each other.
The roller isnít wearing. The pin wears and allows the roller to follow something of an elliptical path as it goes over the cog and chainwheel. New chains follow a circular path so they engage the pitch of the cog and chainwheel properly so they donít wear the edges of the teeth like a chain where the rollers can shift.

The question I have for you is how do your propose to measure roller wear if that is what you think is causing the problem? I can think of no way to measure roller wear separately from pin wear. It is possible, and even quite common, to measure secondary effects to measure a primary phenomena. In chemistry, for example, we often react two chemicals together and then further react the products of that reaction to see what the concentration of the unknown of the first two chemicals are. Pin wear and roller wear are related. Measuring pin wear also measures the effect of the rollers on the cogs.

Frankly, if you are worried about cog wear, you should probably be using one of these. I have one but find them to be mostly useless.
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Old 03-15-23, 10:21 AM
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Originally Posted by cyccommute View Post
The roller isn’t wearing. The pin wears and allows the roller to follow something of an elliptical path as it goes over the cog and chainwheel. New chains follow a circular path so they engage the pitch of the cog and chainwheel properly so they don’t wear the edges of the teeth like a chain where the rollers can shift.

The question I have for you is how do your propose to measure roller wear if that is what you think is causing the problem? I can think of no way to measure roller wear separately from pin wear. It is possible, and even quite common, to measure secondary effects to measure a primary phenomena. In chemistry, for example, we often react two chemicals together and then further react the products of that reaction to see what the concentration of the unknown of the first two chemicals are. Pin wear and roller wear are related. Measuring pin wear also measures the effect of the rollers on the cogs.

Frankly, if you are worried about cog wear, you should probably be using one of these. I have one but find them to be mostly useless.
You mean "sprocket" wear? Because cogs mesh with each other without a chain.

Just kiddin ya
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