When to replace a chain

[Northern Monkey]

Sorry if this is a borderline retarded question,

How do you know it's time to replace a chain?

[MarJay]

Normally when it is worn enough to move side to side rather than just up and down, or if the chain adjustment is at it's limit and the chain has the original number of links.
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[Howling TerrorOutOfOffice]

Another way...with the chain at the correct tension pull the chain from the rear sprocket. If you can see more than half a tooth then the chain is worn.
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[Walloper]

You can tell by pitch extension where you measure the distance between the centre of pin 1 and pin 5. The OEM for the chain will have max pitch in tables somewhere.

Normally a sealed and lubricated chain (O or X-ring chains) do not 'extend' much but the outer surfaces of the rollers wear. This is not as easy to measure without proper tools.

If the sprocket teeth are noticeably worn or becoming 'hooked' then both front and rear sprockets and the chain need to be replaced as they are designed to be matched in wear levels.

If any 'single' part of the 'final drive' is renewed then it will wear very quickly to match the other worn parts before long.
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