Chains, Rollers, Stretch, Checkers, "chain ring test"

wle said:

not meaning to start another big debate, but i have read and read and i
still don;t get it

As intrigueing as this is, let's leave it to Captain Brown to answer.
Come on , Sheldon, show us the way once again!

Sergio
Pisa

wle said:

not meaning to start another big debate, but i have read and read and i
still don;t get it

chains, roller wear, stretching

here is my case

i have a plain shimano 7/8 speed chain, hyperglide, totally stock
no quick release links

i;ve been riding it for 10,000+ miles
it shifts perfectly well
i had been measuring it with a tape measure
it usually measured .35-.45/16" 'stretch'
i even stretch the section i am measuring tight via bungee cords to the
pedals
i thought, well, that is ok, it seems remarkably long lived, but
maybe i just ride lightly, or my extremely casual cleaning technique
works

i got a chain checker
that is where the trouble started
the first thing i noticed was that many sections of chain would measure
fine
but some would indicate more than 1% worn

closer inspection revealed that some of the rollers are very loose on
the pins
also, they have a sort of spinal-disc shape
instead of being flat, they are smaller in the center than the edges

then i started trying to read this group and figure out what to do
which of course didn;t help, too much conflict and 'dunno'

one test i did, was to stretch the chain tight, and see if it engaged
all the teeth on the chain ring

it doesn;t

it acts like a chain that is too long
the top of the chain will be in the valleys, but as it progress down to
the floor, it starts
to rise up out of the valleys

which makes me think it should be replaced, but it;s not too long, and
the R.B.T. wisdom [some of it] said 'roller wear doesn;t matter'

so does it or not?

is the chain ring test the be-all and end-all?

i;ve never seen it recommended by anyone

I think that what you've got is a system that has worn itself to match
over way too many miles of usage; at this point, I doubt that
replacing the chain alone will achieve anything other than making the
wear to the sprockets obvious. The mere fact that your description
pretty much confirms that the rollers are shot (which does change the
effective spacing when under load) is enough to verify that there's a
lot of wear, and sooner or later this will result in a failure. It
might happen in any number of ways, but the only certainty is that it
*will* happen. As for why the measurements aren't revealing any
significant wear, I can't say; I'm not there to look at the way the
numbers are being obtained, so I have to take your word for it that
they are accurate.

In your situation, I would replace no single component immediately,
but I'd begin shopping for replacements for the cassette or freewheel,
the chain, and the front sprockets right away; when they're all in
hand, replace them as a group, and it should work like new again. In
the meantime, if your riding style isn't causing wierd shifting, chain
skipping and the like, smile and cautiously ride on.

--
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Quoted message said:

The mere fact that your description
pretty much confirms that the rollers are shot (which does change the
effective spacing when under load) is enough to verify that there's a
lot of wear, and sooner or later this will result in a failure.

so, you are saying that roller wear has a limit

a. what is the limit then?

b. other experts said, the only thing that matters is chain pitch, and
roller wear doesn;t affect that

wle.

In article <[email hidden]>,

wle said:

so, you are saying that roller wear has a limit

a. what is the limit then?

Well, theoretically you could run the chain until the bushing and pin
wear is so much that the chain breaks under load.

Quoted message said:

b. other experts said, the only thing that matters is chain pitch,
and roller wear doesn;t affect that

Chain wear results in the distance between the pins increasing, which
increases the pitch. Pictures are worth more than words in this case.

Hopefully this will help:

http://pardo.net/bike/pic/fail-004/000.html