RCMoeur 

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...

himespau 

That's why you hang things and let gravity pull the slack out for you.

nomadmax 

This is all I use, accurate and fast.

Lombard

Or better yet, just measure when the chain is on the bike and the derailleur spring is holding it taught.

shelbyfv

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.

himespau 

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.

davidad

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.

davidad

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.

Lombard

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.

RCMoeur 

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.

nomadmax 

Link me the Shimano version and tell me how it's better.

Kontact

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?

Lombard

Precisely. Or rather to replace the chain before you damage the cassette cogs.

davidad

If the chain is not worn the rollers won't effect the cogs. I never said anything about a broken chain.

Kontact

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.

Camilo

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.

Kontact

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?

cyccommute 

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.

Lombard

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.

nomadmax 

Just what I thought, crickets.

Koyote

When in doubt, throw it out.

Kontact

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.

Kontact

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.

cyccommute 

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.

nomadmax 

You mean "sprocket" wear? Because cogs mesh with each other without a chain.

Just kiddin ya