chain un-stretch?

i have been measuring chain stretch on my shimano chain.
8 speed sora components.
i think it;s an "hg" style chain.

i replaced it at 3000 miles.
so these measurements start at 3000 miles.

at 3600 miles, i logged 0.8/16" stretch
at 4000 miles, 1.0/16"
at 4300 miles, 0.1/16"
at 4555, 0.1/16"

you might think there has been a change in measurement procedure.
yes, but if anything, it should measure more lengthening in the
later measurements.
i now put the chain under a lot of tension when measuring this.

i am pretty sure the measurements are right, but what are they measuring?

i do try to keep it pretty clean.

i use the absolute thinnest lubricants, silicone spray and powdered ptfe.

i do ride a lot, probably 100-150 miles a week on that bike.

could it be that dirt or rust or something has built up on the rollers,
taking up the slack for what must still surely be 1/16 worth of wear?

should i just not worry until i can measure 1/16 again?

should i just say, ok, well that chain has gone 1500 miles, time to
replace it, if it;s gone that long and is measuring all screwy like that?

wle.

larry english wrote:


could it be that dirt or rust or something has built up on the rollers,
taking up the slack for what must still surely be 1/16 worth of wear?

That's certainly possible in theory, there is a comprehensive web page
on the subject of chain suck which aruges convincingly (to me) that
dirt-induced chain 'shrink' can be a major factor in this phenomenon
(typically when a new chain is used on slightly worn chainrings, a
mistake I have made in the past). This is however more likely with muddy
MTB conditions, I couldn't say how likely it is to be the case in your
situation.

James

James Annan wrote in message ...
larry english wrote:


could it be that dirt or rust or something has built up on the rollers,
taking up the slack for what must still surely be 1/16 worth of wear?

That's certainly possible in theory, there is a comprehensive web page
on the subject of chain suck which aruges convincingly (to me) that
dirt-induced chain 'shrink' can be a major factor in this phenomenon
(typically when a new chain is used on slightly worn chainrings, a
mistake I have made in the past). This is however more likely with muddy
MTB conditions, I couldn't say how likely it is to be the case in your
situation.

right, there has been zero mud, and i am not using a sticky or
gunky lube.

wle.


James