new chain

Quoted post said:

Originally posted by Smmb
OK, anticipating flames ...

I know that the new chain I just put on is skipping because I have to change the cassette. But how
about explaining how the old chain ran with the cassette with no skipping. I am sure it's too
obvious an answer, but I don't know it.

--

Sandy Paris FR

*******

La vie, c'est comme une bicyclette, il faut avancer pour ne pas perdre l'équilibre. -- Einstein, A.

"This chain and sprocket have worn together. You can see daylight under the chain in some places. The worn chain has "stretched" so that it no longer matches the original pitch of the sprocket. The sprocket has worn so as to effectively increase its pitch to match the worn chain."
From Sheldon Brown's site at URL:
http://sheldonbrown.com/chains.html

SMMB said:

OK, anticipating flames ...

I know that the new chain I just put on is skipping because I have to change the cassette. But how
about explaining how the old chain ran with the cassette with no skipping. I am sure it's too
obvious an answer, but I don't know it.

Look at:

sheldonbrown.comchains.htmlOpen ↗

Answer to your specific question is about 2/3 of the way down the page

Tom

SMMB said:

OK, anticipating flames ...

I know that the new chain I just put on is skipping because I have to change the cassette. But how
about explaining how the old chain ran with the cassette with no skipping. I am sure it's too
obvious an answer, but I don't know it.

It's a very good question, and the answer is far from obvious. Back in the late 70's, it took me a
couple of years to work it out - the local bike shops didn't know.

In recent times, I was delighted to discover that Sheldon came up with the same answer
(sheldonbrown.comchains.htmlOpen ↗ to repeat Tom's reference to it).

John

tcmedara said:

SMMB said:

OK, anticipating flames ...

I know that the new chain I just put on is skipping because I have to change the cassette. But
how about explaining how the old chain ran with the cassette with no skipping. I am sure it's too
obvious an answer, but I don't know it.

Look at:

sheldonbrown.comchains.htmlOpen ↗

Answer to your specific question is about 2/3 of the way down the page

Tom

Very good link, but I notice Sheldon recommends replacing the chain early before the
freewheel/cassette is worn out. I seem to always forget and only realize my chain is worn out when
the SIS starts acting up after about 3000 miles of road use.

Would your Freewheels/cassette last twice as long if you replaced the chain three times at 1500 mile
intervals without replacing the freewheel/cassette?

How does chain stretch effect chain ring life? I have replaced several freewheel and chain combos
but my chainring teeth still seem to be fine.

daveornee said:

"This chain and sprocket have worn together. You can see daylight under the chain in some places.
The worn chain has "stretched" so that it no longer matches the original pitch of the sprocket.
The sprocket has worn so as to effectively increase its pitch to match the worn chain." From
Sheldon Brown's site at URL: sheldonbrown.comchains.htmlOpen ↗

But the crucial thing is the change in tooth profile, such that a correctly-pitched chain can
no longer slip past the head of the tooth where the relatively loose chain is being fed onto
the sprocket.

John

Earlier said:

But the crucial thing is the change in tooth profile, such that a correctly-pitched chain can no
longer slip past the head of the tooth where the relatively loose chain is being fed onto the
sprocket.

For what it's worth, here's my attempt at a diagram of the area where the chain is trying to mesh
with a worn tooth. View with a fixed font for this to make any sense.

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

/|\ /|\
| |
A B

"A" represents the line of the bushing on a new chain trying to mesh with the worn sprocket, and "B"
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).

In my student days, I used to recondition my old 5-speed freewheels by dismantling them and
machining off that overhanging part on all the teeth of the affected sprockets.

John