Originally Posted by
Gresp15C
When I think I'm ready to replace a chain, I hang the old and new chains side by side. Over the full length of a chain, the elongation becomes pretty obvious.
Here's that process (new chain on the right). There's no doubt about the elongation. FWIW, the old chain was flagged by three different chain checker tools.
Chains hanging from nails on a level line
Worn chain on the left
Three chain-check tools. The Shimano tool (right) is supposedly not influenced by roller wear.