On Friday, December 22, 2017 at 6:53:15 PM UTC-5, Emanuel Berg wrote:
Frank Krygowski wrote:

Chain wear happens inside the chain's pivots.
The wear is on the pins, the rollers and any
surface between them.

The wear happens when the pivot is under
tension and the two links connected by that
pivot are either bending or straightening.

OK...? Do you have a picture that illustrates
this or at least identifies the parts refered
to? I have this

http://user.it.uu.se/~embe8573/bike/...erminology.jpg

but "pivot" isn't mentioned...

By pivot, I meant the pin and the plates attached to it. The part that acts as a
hinge. The point is, to get wear in the chain, you need pressure on the surfaces
in contact, and you need relative motion between those surfaces.

And how long should you be able to go before
the slack exposes you a fraud mechanic
and/or the owner of crooked gear?

For derailleur bikes, many people recommend
replacing a chain when it's worn (or
"stretched") so it's one half percent longer
than when new. (This is most easily measured
with a ruler marked in inches. Do you have
one of those?)

Eheh... what's next, you going to ask Picasso
if he has a brush? Of course I have folding
rule, ruler, measuring tape, and calipers in
inches as well as cm.

Well, I didn't know. In the U.S. it's not unheard of for people to have no
ruler that measures in centimeters.

But you have to remove the chain to do this,
right?

Not usually. It's most easily done with the chain on the bike. Just use the
cranks to apply a little tension.

So it is not so fast after all.
Even less so with a chain guard which is very
common on these bikes.

If the chainguard totally encloses the chain, then yes, it's more trouble. OTOH,
if you have a totally enclosed chain, it will probably last as long as the bike.

- Frank Krygowski