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 lyrictenor1 02-27-14 03:26 PM

Stupid question about checking chain wear

Sorry for the stupid question. I have done a search and have not found this addressed: I have a Spin Doctor chain wear indicator (knockoff of the Park Tool one), and get a different reading between having the chain on the small chainring and the large chainring (both with the chain in the middle of the cassette). Which chainring should I be using when checking for wear?

 Andy_K 02-27-14 03:48 PM

That's actually a really good question. I had never thought to look for differences between gears. I guess chain tension could effect the reading. How much difference are you seeing?

 lyrictenor1 02-27-14 03:59 PM

Quote:
 Originally Posted by Andy_K (Post 16533129) That's actually a really good question. I had never thought to look for differences between gears. I guess chain tension could effect the reading. How much difference are you seeing?

When in the small chaining, the indicator won't slide all the way down to the detent of the tool's 0.75mm indicator. In the large chaining, the tool will easily slide down into the 0.75mm detent. The chain is in the middle of the cassette for both chainring positions.

 DiabloScott 02-27-14 04:49 PM

It doesn't make any difference.

You're either doing something wrong, or you're doing something inconsistently, or you've got some really wonky chain wear.

 FBinNY 02-27-14 04:51 PM

The choice of chainrings doesn't matter, but to get consistent readings you have to put some tension into the chain. I always measure the lower loop while pulling the RD back to put a few pounds of tension into the chain.

Even then you might get various readings because the chain doesn't always wear uniformly. Variations in metallurgy and lubrication can cause some links to wear faster than others. You're getting an average, and the larger the sample the more consistent the reading will be. That's a good argument for a 12" ruler vs. a tool that measures over 4" or so.

 lyrictenor1 02-27-14 05:11 PM

Quote:
 Originally Posted by FBinNY (Post 16533308) The choice of chainrings doesn't matter, but to get consistent readings you have to put some tension into the chain. I always measure the lower loop while pulling the RD back to put a few pounds of tension into the chain.

Thanks! In most of the instructions I've read, there really hasn't much mention in regards to tension. Thanks for the info.

 FBinNY 02-27-14 05:27 PM

Quote:
 Originally Posted by lyrictenor1 (Post 16533352) Thanks! In most of the instructions I've read, there really hasn't much mention in regards to tension. Thanks for the info.
I'm not talking about much tension, just enough to ensure all slack is pulled out.

Imagine a long freight train. After the engines stop all the cars move forward in the space the couplers allow. When the engines pull out again the cars move forward one at a time taking up the slack in the couplers. If you live anywhere near where trains start or stop you can hear the clack, clack, clack of both events.

So now measure the length of the train. You'll get very different results after it stops vs. when it first pulls out.

Same with the chain, though on a much smaller scale.

 Looigi 02-28-14 10:24 AM

FWIW: Most all chain tools preferential measure roller wear which is much less important that pin/bushing wear which is what contributes chain elongation. Here's a newly introduced chain measuring tool that works correctly: http://pedros.com/pedros-new-chain-c...n-grease-plus/

And for a technical discussion: http://pardo.net/bike/pic/fail-004/000.html

A good ruler still works fine.

 FBinNY 02-28-14 10:45 AM

Quote:
 Originally Posted by Looigi (Post 16535291) FWIW: Most all chain tools preferential measure roller wear which is much less important that pin/bushing wear ....... .
It's a popular misconception that roller wear is less important than pin wear. In reality it's possibly more important. Worn rollers allow the chain to ride closer to the center of the sprocket. Since circumference is 6 times radius, so moving closer to the center by 0.001" shortens the effective sprocket pitch by 0.006". Shortening sprocket pitch, or lengthening chain pitch are two sides of the same coin.

That said, however ou measure the chain, you're not measuring wear directly, since there are complex wear factors. What you're getting is an estimate of the chains condition based on assumptions about the normal wear patterns.

Years ago, before bushingless chains, chains could safely be used until they stretched to the 1% wear point. These days most people use 1/2% as the replacement point. I suspect that the higher ratio of roller wear to pin wear on modern chains accounts for the shortening of the guideline. I do know for a fact, that chains can be worn to a point where they eat sprockets even with very little stretch, because of a higher than average roller/pin wear ratio.

That said, I still prefer using a ruler than any of the gadgets,
A because I already own one,
B because it measures a larger sample, doing a better job averaging variations in wear
C because the 1/2% guideline is based on only pin wear, and adding roller wear as the gadgets causes premature chain replacement.

That said, understand that chains vary in the roller/pin wear ratio, so you may want to adjust your replacement point. For example Campagnolo chains seem to last very long when measured for stretch, but the rollers an be severely worn well before they reach the 1/2% mark.

 noglider 02-28-14 11:25 AM

Just replace the chain. ;)

 FBinNY 02-28-14 11:29 AM

Quote:
 Originally Posted by noglider (Post 16535518) Just replace the chain. ;)
Of course that's always an option. The question remains when is the best time to replace one based on the economics of chain and sprocket cost. Then the second question, how to determine - how to know where the chain is on that time line.

 noglider 02-28-14 11:36 AM

Of course that's true. After all, I don't replace my chain every week. But if there is doubt, I replace it. Life is so much better.

 3alarmer 02-28-14 01:00 PM

Quote:
 Originally Posted by Looigi (Post 16535291) And for a technical discussion: http://pardo.net/bike/pic/fail-004/000.html A good ruler still works fine.

 3alarmer 02-28-14 01:07 PM

..just as an afterthought, I've been using KMC chains almost exclusively for about the last five years.

They seem to work on everything I've tried them on, and I don't have to worry about the various directional
shear pins and orientation of them that kinda put me off of Shimano chains. The fact that they come in an
endless variety of finishes and grades at competitive prices has not hurt my feelings, either.

But it is true that most of what I own and work on is eight cog or less in the rear. Am I missing something
important when I recommend KMC as the chain of choice to the people who ask me about them ?

 noglider 02-28-14 02:06 PM

KMC chains haven't failed me yet. It makes you wonder why they cost less than all the others, but I don't know anyone who has found fault in them. Go KMC!

 Looigi 03-02-14 11:10 AM

Quote:
 Originally Posted by FBinNY (Post 16535371) It's a popular misconception that roller wear is less important than pin wear. In reality it's possibly more important. Worn rollers allow the chain to ride closer to the center of the sprocket. ...
Disagree, but not interested in debating. Anyone interested can easily research the matter and come to their own conclusions.

The best tool to measure chain wear is a ruler. I have a chain checker and use it, but when it is time to replace a chain I always use a ruler.

 Drew Eckhardt 03-03-14 11:42 AM

Quote:
 Originally Posted by FBinNY (Post 16535371) That said, understand that chains vary in the roller/pin wear ratio, so you may want to adjust your replacement point. For example Campagnolo chains seem to last very long when measured for stretch, but the rollers an be severely worn well before they reach the 1/2% mark.
Campagnolo allows a maximum of 132.60mm (5.220") between the starting and ending rollers of six consecutive outer half-links.

(Their 112 page 10-speed chain instruction manual mentions this in six different languages)

 FBinNY 03-03-14 12:04 PM

Quote:
 Originally Posted by Drew Eckhardt (Post 16544208) Campagnolo allows a maximum of 132.60mm (5.220") between the starting and ending rollers of six consecutive outer half-links.
Yes, this is a combined guideline factoring both pin and roller wear. If one considers, it weighs roller wear 6x more than pin wear, which matches the logic that a change in effective radius is worth 6x a change in circumference. (see my prior post explaining the logic)

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