On Tuesday, December 19, 2017 at 4:07:53 PM UTC+1, Frank Krygowski wrote:
On 12/19/2017 1:05 AM, Emanuel Berg wrote:
Frank Krygowski wrote:

If you're starting from a stop by applying
extra torque to the cranks (as is usual) you
would get extra wear at that moment. But it's
only for a moment. I suspect it has little
overall effect.

OK, so when and why does wear occur?

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.

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?) But for a bike with only one rear cog, I think can go
much longer.

I'd say if the chain on a single speed or hub gear bike doesn't skip
when you pedal your hardest, it's probably OK. We'll see if others disagree.

On a single speed you have the same wear criteria as with derailleur system if you want to replace the chain without replacing the cog or chainring. If you accept that you have to replace the cog and/or chainring when you replace the chain than you can go on until you can't tension the chain anymore or the teeth are completely gone.

Lou