Time for a new chain?

Pat Lamb writes:

I agree and besides, don't try to use the method shown on some web
sites (finding the edge of a pin). Align an inch mark of a
yardstick with the center of a chain pin and glance at the inch
mark 12 inches away. The accuracy of this is easy to assess by
glancing back and forth between the reference pin and the one
downstream to see if the yard stick has moved. Eyeball centering
is good enough for this qualitative assessment. We aren't
interested in how many 0.001" too long the chain is, but rather
whether it is out of reasonable limits. Don't take the 1/16"
number as absolute. It is a reasonable number.

What may be less apparent is that chain elongation affects only
every second roller and therefore the effect is greater (2x) than
the percentage measured. Every pair of rollers in an inner link
remains at exactly 1/2" while the pins and sleeves wear to cause
interlink elongation.

It took me a while to figure out what you meant by "elongation
affects only every second roller" and I'm still not sure if you're
right. I think you're ascribing all the wear to the pin/plate
junctions. Are you sure there's not significant wear going on at
the roller to inner plate swage junction?

The inner link side plate does not change length and both rollers wear
on its sleeves equally giving them more clearance but still at the
same spacing.

On Sheldon's chain page

http://sheldonbrown.com/chains.html)

the chain wear picture

http://sheldonbrown.com/images/chain_wornbush.gif

shows the swaged part has worn on the inside, which would
effectively increase that 1/2" pitch.

Both rollers do that so under load they are still 1/3 inch apart. In
contrast, chain tension lengthens the chain so that the distance
between pins grows with wear.

Jobst wrote:

What may be less apparent is that chain elongation affects only every
second roller and therefore the effect is greater (2x) than the
percentage measured. Every pair of rollers in an inner link remains
at exactly 1/2" while the pins and sleeves wear to cause interlink
elongation.

Pat Lamb wrote:

It took me a while to figure out what you meant by "elongation affects
only every second roller" and I'm still not sure if you're right.

He's right, but could have expressed himself more clearly. Elongation
doesn't affect the rollers, it affects _pairs_ of rollers.
Specifically, it's the roller pairs connected by outer plates.

I think you're ascribing all the wear to the pin/plate junctions.

That's the only part of the wear that affects the pitch of the chain.

Are you
sure there's not significant wear going on at the roller to inner plate
swage junction? On Sheldon's chain page
(http://sheldonbrown.com/chains.html) the chain wear picture
(http://sheldonbrown.com/images/chain_wornbush.gif) shows the swaged
part has worn on the inside, which would effectively increase that 1/2"
pitch.

No, that wear happens to each roller, so it doesn't affect the distance
between them, i.e., the pitch.

Sheldon "Pitch Pictures" Brown
+--------------------------------------------------------+
| There is no conclusive evidence of life after death. |
| But there is no evidence of any sort against it. |
| Soon enough you will know, so why fret about it? |
| --Robert A. Heinlein |
+--------------------------------------------------------+
Harris Cyclery, West Newton, Massachusetts
Phone 617-244-9772 FAX 617-244-1041
http://harriscyclery.com
Hard-to-find parts shipped Worldwide
http://captainbike.com http://sheldonbrown.com

On Mon, 13 Jun 2005 19:51:18 GMT, wrote:

What may be less apparent is that chain elongation affects only every
second roller and therefore the effect is greater (2x) than the
percentage measured. Every pair of rollers in an inner link remains
at exactly 1/2" while the pins and sleeves wear to cause interlink
elongation.

Won't the interface roller/sleeve wear as well, so allowing the roller to
move about in all directions?

Jasper

Alex Rodriguez wrote:
In article .com,
says...
Following the reasoning in this thread, that 12 1/16 (12,0625) inches
measured warrants a new chain...

Chuck the park tool and just measeure with a ruler. Then you won't be
confused.

I missed this the first time around.

Nail a yardstick vertically to the wall of your workshop. Now it's
always ready for a quick check of the chain when the chain is being
cleaned. Vertical orientation is important so that the weight of the
chain pulls the links taut during the measurement.

--
Dave
dvt at psu dot edu

Jasper Janssen writes:

What may be less apparent is that chain elongation affects only
every second roller and therefore the effect is greater (2x) than
the percentage measured. Every pair of rollers in an inner link
remains at exactly 1/2" while the pins and sleeves wear to cause
interlink elongation.

Won't the interface roller/sleeve wear as well, so allowing the
roller to move about in all directions?

This is a logic problem. Give it some thought. The distance between
centers of rotation of a roller pair do not change. They are on the
same (chain) side plate and their wear is the same.