New Chains

I've been told it's essential to replace chain and sprokets at the same time
What happens if you fit a new chain to old sprockets?

Ken

..

Ken wrote:

I've been told it's essential to replace chain and sprokets at
the same time What happens if you fit a new chain to old
sprockets?

A new chain will work fine on old sprockets as long as sprocket
wear isn't excessive. If the sprocket teeth have developed a
wear pocket (not always visible to the eye), then the new chain
will periodically skip forward by one tooth under load.

Replacing chains when wear reaches 0.1mm elogation per link will
mean that sprockets last a long time (many chains).

John

Depends how worn the old chain was. Hang the old chain up and use a good
steel rule to measure how long 24 links are. If they have worn to measure
12-1/8" or more, then I would replace both chain and cassette, as the new
chain and old cassette won't mesh well together. 1/8" is approximately 1%
wear.

"Ken" wrote in message
...
I've been told it's essential to replace chain and sprokets at the same
time
What happens if you fit a new chain to old sprockets?

Ken

.

John Henderson wrote:

Ken wrote:

I've been told it's essential to replace chain and sprokets at
the same time What happens if you fit a new chain to old
sprockets?

A new chain will work fine on old sprockets as long as sprocket
wear isn't excessive. If the sprocket teeth have developed a
wear pocket (not always visible to the eye), then the new chain
will periodically skip forward by one tooth under load.

Replacing chains when wear reaches 0.1mm elogation per link

How do you test this?

Steve = : ^ )

Steve Ball wrote:

John Henderson wrote:

Replacing chains when wear reaches 0.1mm elogation per link

How do you test this?

Like Nick says, 24 links at 1/2" each should measure 12".
Measured with a good ruler, 1/8" elongation over 12" is the
wear limit.

I cheat and use a Rohloff chain checker:
http://www.rohloff.de/en/products/caliber_2/index.html I
prefer using this to a ruler. Park Tools also makes a version:
http://www.parktool.com/products/det...=5&item=CC%2D3

Because a badly worn chain doesn't distribute the load over
multiple sprocket teeth, it causes rapid sprocket wear.

John

John Henderson wrote:
Steve Ball wrote:

John Henderson wrote:

Replacing chains when wear reaches 0.1mm elogation per link
How do you test this?

Like Nick says, 24 links at 1/2" each should measure 12".
Measured with a good ruler, 1/8" elongation over 12" is the
wear limit.

I cheat and use a Rohloff chain checker:
http://www.rohloff.de/en/products/caliber_2/index.html I
prefer using this to a ruler. Park Tools also makes a version:
http://www.parktool.com/products/det...=5&item=CC%2D3

Because a badly worn chain doesn't distribute the load over
multiple sprocket teeth, it causes rapid sprocket wear.

John

I've got a Park Chain check tool that checks for 0.75% and 1%
wear. I usually replace my chain before it gets to 0.75% - chains
are cheap compared to cassettes.

My test now is as follows:
Get out a set of vernier calipers
Set distance between tines to 132mm
Insert tines into chain links.
Extend calipers
If distance is greater than 132.6mm, replace chain
This represents about 0.5% stretch.

Note, this method comes from the Campagnolo instructions
for their 10sp chain. Since all bicycle chains have the
same pitch, it works on all chains.

DeF

--
e-mail: d.farrow@your finger.murdoch.edu.au
To reply, you'll have to remove your finger.

Ken wrote:

I've been told it's essential to replace chain and sprokets at
the same time What happens if you fit a new chain to old
sprockets?

I've found an ASCII diagram I once did to help show why a new
chain skips on a worn sprocket. View with a fixed (not
proportional) font for this to make proper sense.

\ /
| |
| |
| \
| |
| /
\___/

/|\ /|\
| |
N W

"N" represents the line taken by the bushing on a new chain
trying to mesh with a worn sprocket tooth as it's fed onto it.
And "W" represents the line of the corresponding part on a worn
chain. We're looking at a tooth on the bottom of the sprocket,
rotating clockwise (ie, towards the left).

The reason the new chain link is committed to line "N" is that
it's sitting in the pockets of the teeth it's already engaged
with (having been pulled into those pockets by peddling
pressure). And it doesn't have enough "stretch" to allow it to
move over and follow line "W" into the gap between teeth. So
every now and then, the chain rides up over the top of a tooth
all the way from meeting the sprocket at the bottom to leaving
it at the top.

That the hook (the unworn material towards the head of the
tooth) is the problem can be demonstrated by removing it (on
all teeth of that sprocket) with a grinder. The skipping
disappears. But this is only a temporary repair, as the
case-hardening is gone.

John