Chain "Stretch" - Part 3 (diagrams)

After talking to a few friends trying to explain "chain stretch" I have decided a picture is worth a thousand words... so I built a few illustrations showing chain wear.

The pin, showing in black, wears away by rubbing the (orange) housing. This creates a looseness that increases its length.

When the chain is longer it rides up on the teeth of the gear reducing the contact, allowing it to "skip" under hard pedaling.  It will also wear the tooth away when it rides the incorrect location of the tooth, effectively eating it away.

So keep your chain clean and lubricated. And replace it when it gets "stretched."

Part 1: Measuring Chain Stretch
Part 2: Free Wheel Removal
Part 3 (this post): Chain Stretch Diagrams