Chain measurements and wear

[cnighbor1]

Why are chains measured in inches and not cm or mm? Every thing else is in cm and mm. I refer to below
Measuring Chain Wear

''The standard way to measure chain wear is with a ruler or steel tape measure. This can be done without removing the chain from the bicycle. The normal technique is to measure a one-foot length, placing an inch mark of the ruler at the side of one rivet, then looking at the corresponding rivet 12 complete links away. On a new, unworn chain, this rivet will also line up exactly with an inch mark. With a worn chain, the rivet will be past the inch mark. [For accurate measurement, the chain should be held under some tension -- either on the bicycle, or hanging. -- John Allen]
This gives a direct measurement of the wear to the chain, and an indirect measurement of the wear to the sprockets:
•If the rivet is less than 1/16" past the mark, all is well.
•If the rivet is 1/16" past the mark, you should replace the chain, but the sprockets are probably undamaged.
•If the rivet is 1/8" past the mark, you have left it too long, and the sprockets (at least the favorite ones) will be too badly worn. If you replace a chain at the 1/8" point, without replacing the sprockets, it may run OK and not skip, but the worn sprockets will cause the new chain to wear much faster than it should, until it catches up with the wear state of the sprockets.
•If the rivet is past the 1/8" mark, a new chain will almost certainly skip on the worn sprockets, especially the smaller ones.''
charles

[flydhest]

Because gearing is measured in gear-inches. If you want to measure your chain in millimeters, you have to first convert your gearing to gain ratios, then the chain measurement will work, but I think you have to divide by pi.

[Chief]

Because gearing is measured in gear-inches. If you want to measure your chain in millimeters, you have to first convert your gearing to gain ratios, then the chain measurement will work, but I think you have to divide by pi.


Gearing is equal to the diameter of the wheel times the ratio of the number of teeth on the chain ring to the number of teeth on the cog. It has nothing to do with the length of the chain or whether the chain length is measured in inches, cm, mm or any other unit. The chain is measured in inches because of the tradition for machining gears.

[Kontact]

You can measure it in metric, but my ruler doesn't have 25.4mm marks.

Most things on bikes are still derived from Imperial measures, which is why you see "31.8" and "28.6" on so much stuff. Hardware is now metric, as are tires, but chain pitch and tube diameters were standardized by English speakers a long time ago.

Maybe Shimano will bring back its 10mm pitch chain for you.

[flydhest]

Gearing is equal to the diameter of the wheel times the ratio of the number of teeth on the chain ring to the number of teeth on the cog. It has nothing to do with the length of the chain or whether the chain length is measured in inches, cm, mm or any other unit. The chain is measured in inches because of the tradition for machining gears.

Dude, really? You took that seriously? Even after the divide by pi?



Really?

[witcombusa]

Just use the Park chain wear go/no go gauge....done

[fiataccompli]

exactly...I don't measure in Imperial or Metric units, I measure in binary units with the Park gauge...yes or no

[Louis]

Just use the Park chain wear go/no go gauge....done

+1 Works for me.

Some folks make this incredibly complicated, rotating a whole bunch of chains through the drive-train. Overkill IMO. When several locations on a given chain show more than 0.75% I change it.

From the Park web site:

A worn chain shifts poorly and wears sprockets at an accelerated rate. The CC-3.2 is a “go-no go” gauge designed to accurately indicate when a chain reaches .5% and .75%, the points at which most chain manufacturers suggest replacement. The updated CC-3.2 is longer, more accurate and features permanent measurement markings.

[Dave]

The standard chain pitch is .500 inch, not some metric unit of measure.

Anyone who understand chain wear knows that a Park chain checker is extremely inaccurate. It will tell you that a brand new Shimano chain has about .25% elongation, but of course it does not. The error is casued by differences in the roller diameter and clearances between the roller and the bushing formed into the inner side plates. Even if you subtract that initial error, you get more error as the chain wears. The Park tool measures over a short length, where the roller wear can easily equal the true increase in elongation, so the reading can still have a large error. Elongation is properly measured between the pins, with no contribution from the rollers. A precision 12" machinist's rule works great for measuring chain wear.

Campy chains wear differently than most other brands and often show very little elongation, even after 6,000 miles of use. Unfortunately, that does not mean that the chain is in good shape and good for more use. If may be totally shot and already caused enough cog wear to cause new-chain skip, if a new chain is installed. That's where the idea of using several chains in a rotation comes from. It will eliminate new-chain skip and allow more use from a cassette.

With Campy 11 speed, I think that 3 chains, each used for 4,000 miles with one cassette is a respectable life.

[Kontact]

The standard chain pitch is .500 inch, not some metric unit of measure.

Anyone who understand chain wear knows that a Park chain checker is extremely inaccurate. It will tell you that a brand new Shimano chain has about .25% elongation, but of course it does not. The error is casued by differences in the roller diameter and clearances between the roller and the bushing formed into the inner side plates. Even if you subtract that initial error, you get more error as the chain wears. The Park tool measures over a short length, where the roller wear can easily equal the true increase in elongation, so the reading can still have a large error. Elongation is properly measured between the pins, with no contribution from the rollers. A precision 12" machinist's rule works great for measuring chain wear.

Campy chains wear differently than most other brands and often show very little elongation, even after 6,000 miles of use. Unfortunately, that does not mean that the chain is in good shape and good for more use. If may be totally shot and already caused enough cog wear to cause new-chain skip, if a new chain is installed. That's where the idea of using several chains in a rotation comes from. It will eliminate new-chain skip and allow more use from a cassette.

With Campy 11 speed, I think that 3 chains, each used for 4,000 miles with one cassette is a respectable life.

If there is no elongation, and roller wear is not important, how is it wearing the cogs?

[oldpotatoe]

Why are chains measured in inches and not cm or mm? Every thing else is in cm and mm. I refer to below
Measuring Chain Wear


Why are ball bearings measured in inches? 1/4 inch ball bearing? Even in Europe?

Why are a lot of European road tires, 700c, called '28 inch?

Scientists do not know.

[Mark McM]

Why are chains measured in inches and not cm or mm? Every thing else is in cm and mm. I refer to below
Measuring Chain Wear

''The standard way to measure chain wear is with a ruler or steel tape measure. This can be done without removing the chain from the bicycle. The normal technique is to measure a one-foot length, placing an inch mark of the ruler at the side of one rivet, then looking at the corresponding rivet 12 complete links away. On a new, unworn chain, this rivet will also line up exactly with an inch mark. With a worn chain, the rivet will be past the inch mark. [For accurate measurement, the chain should be held under some tension -- either on the bicycle, or hanging. -- John Allen]
This gives a direct measurement of the wear to the chain, and an indirect measurement of the wear to the sprockets:
•If the rivet is less than 1/16" past the mark, all is well.
•If the rivet is 1/16" past the mark, you should replace the chain, but the sprockets are probably undamaged.
•If the rivet is 1/8" past the mark, you have left it too long, and the sprockets (at least the favorite ones) will be too badly worn. If you replace a chain at the 1/8" point, without replacing the sprockets, it may run OK and not skip, but the worn sprockets will cause the new chain to wear much faster than it should, until it catches up with the wear state of the sprockets.
•If the rivet is past the 1/8" mark, a new chain will almost certainly skip on the worn sprockets, especially the smaller ones.''
charles

To get back to the original question:

1/2" was the original standard for bicycle chain pitch. In the intervening years since this was standardized, the international standard for the length of the inch has been defined as exactly 25.4 mm. This means that 1/2" is exactly 12.7 mm, and either designation may be correctly used for bicycle chains.

As far as measuring chain wear in fractions of an inch over 12", that is just a convenient method using commonly available measuring tools. 12" rulers are very common in the US, as are 36" yard sticks. These measuring tools are commonly graduated in 1/8" and/or 1/16" units. Tolerances of 0.5% and 1% elongation are commonly used measures for chain and/or sprocket replacement, and it just so happens that 1/16" is very close to 0.5% of 12", and 1/8" is very close to 1% or 12" (actual percentages are 0.52% and 1.04%).

Why are ball bearings measured in inches? 1/4 inch ball bearing? Even in Europe?

Bearing balls are commonly available in both millimeter and inch dimensions. Both in the US and in Europe.

[Dave]

If there is no elongation, and roller wear is not important, how is it wearing the cogs?

Who said that roller wear is not important? All I've said is that roller wear is NOT the same as an increase in pitch. Roller wear is huge, compared to the wear that causes chain elongation and the two cannot be compared as equals.

If a chain elongates by .5% or more, along with a significant amount of roller wear, then the chain gets changed out and roller wear is never even considered. A Shimano chain will typically show an increase in roller spacing around .025 inch, when it also has .5% elongation.

The rollers on a Campy chain don't wear much better than the other brands, but the pin/bushing wear (true elongation or change in pitch) is much less. If a Campy chain is kept in use for perhaps twice as long as a Shimano chain and still shows little elongation, the sprocket teeth still wear and conform to the smaller diameter of the worn rollers. The roller spacing on a Campy chain, used for 6,000 miles may show an increase of .040 inch. The result will be similar to using another brand of chain, well past the recommended replacement point of .5% elongation. You're likely to get chain skip on one or more of the most-used cogs.

The bottom line is that measuring only elongation works fine for chains that elongate quickly, but not for those that do not. With a Campy chain that is well maintained, measuring elongation is of no value. I only monitor the roller spacing. If you want to get 2-3 chains worth of use from a cassette, then toss the chain when the roller spacing increases to around .025. Rather than do that, I alternate several chains and change to a different one when the roller spacing increases by about .020 inch. I can run each chain until the roller spacing increase by .035-.040 and never have to worry about chain skip.

[Kontact]

Who said that roller wear is not important? All I've said is that roller wear is NOT the same as an increase in pitch. Roller wear is huge, compared to the wear that causes chain elongation and the two cannot be compared as equals.

If a chain elongates by .5% or more, along with a significant amount of roller wear, then the chain gets changed out and roller wear is never even considered. A Shimano chain will typically show an increase in roller spacing around .025 inch, when it also has .5% elongation.

The rollers on a Campy chain don't wear much better than the other brands, but the pin/bushing wear (true elongation or change in pitch) is much less. If a Campy chain is kept in use for perhaps twice as long as a Shimano chain and still shows little elongation, the sprocket teeth still wear and conform to the smaller diameter of the worn rollers. The roller spacing on a Campy chain, used for 6,000 miles may show an increase of .040 inch. The result will be similar to using another brand of chain, well past the recommended replacement point of .5% elongation. You're likely to get chain skip on one or more of the most-used cogs.

The bottom line is that measuring only elongation works fine for chains that elongate quickly, but not for those that do not. With a Campy chain that is well maintained, measuring elongation is of no value. I only monitor the roller spacing. If you want to get 2-3 chains worth of use from a cassette, then toss the chain when the roller spacing increases to around .025. Rather than do that, I alternate several chains and change to a different one when the roller spacing increases by about .020 inch. I can run each chain until the roller spacing increase by .035-.040 and never have to worry about chain skip.
So, you measure roller wear with a Park chain tool, or something else?

[Dave]

So, you measure roller wear with a Park chain tool, or something else?

I use the internal measuring tips of my dial calipers. I want a real value for the change in the spacing.

The space between Campy rollers will be .200-.205 inch when new and Shimano/KMC will be in the .210-.215 inch range. That does not make a new Shimano or KMC chain partially worn or elongated.