Originally Posted by
Kontact
Chain checker trumps a ruler. You're attempting to avoid wearing out your sprockets, and sprockets run on the rollers the checker measures, not the pins a ruler measures.
And this is what that looks like when there is no pin stretch (ruler) but roller wear:
The rollers are not a factor in measuring chain wear. The "stretch" comes between the pins and the inner plates that act as bushings. Nice drawing though.