[QUOTE=arregi;1324442]Im no mechanical engineer but the the center to center distances from to pin to pin seem larger in an old chain and i think that will mean stretch.
/QUOTE]
that's because they are. the effective pitch of the chain increases, which wears the chainring and cog to fit the new pitch, but it is not due to the link plates stretching.
[QUOTE=arregi;1324442]Im no mechanical engineer but the the center to center distances from to pin to pin seem larger in an old chain and i think that will mean stretch.
/QUOTE]
that's because they are. the effective pitch of the chain increases, which wears the chainring and cog to fit the new pitch, but it is not due to the link plates stretching.