If your chainring/sprocket is worn then it'll ruin the new chain. And if you get a new chainring/sprocket with an old chain then it'll wear out the new bits.
All depends how much you care about it.
@O'Shane started
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If your chainring/sprocket is worn then it'll ruin the new chain. And if you get a new chainring/sprocket with an old chain then it'll wear out the new bits.
All depends how much you care about it.