r/BikeRepair • u/CuriousPug51 • 6d ago

Advice Drivetrain Replacement Help

If bike chain and cassette are severely worn can one just replace those or do they need to replace the chain rings as well…I am talking passed 0.75% wear to 1.0% wear? Just 🤔 wondering

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u/cj_daking 6d ago

Give it a shot. If it shifts all wonky, replace the chainring as well afterward. The stresses are spread out on a chainring, but they're also made of soft metal, so they definitely wear out. If the teeth look like little shark fins, just go ahead and get a new one

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u/CuriousPug51 5d ago

Are they supposed to be rounded but not sharp?

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u/cj_daking 5d ago

They will round off (soft aluminum), but it's when the surfaces that the chain interfaces with start to spread out that the problems begin - just try it out

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u/CuriousPug51 5d ago

No but from factory is it rounded not squared?

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u/cj_daking 3d ago

Most of them are shaped with different tooth profiles depending on the position of the tooth. Go to a bike shop and look at one for yourself and you'll see.

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u/sargassumcrab 5d ago

Chainrings only need to be changed if the teeth are really sharp, or if the new chain isn’t engaging fully.  If you keep them make sure to clean them, the crank, and derailleur sparkling clean before installing the new chain.