velorution:

Sometimes when our mechanic replaces the chain while servicing a bike, it elicits the reaction: “Why did you replace it? It was working fine”.

Here are a few notes to explain why changing the chain saves money.

Why the chain wears:
The chain is made of 100-114 links; each one has two plates , a rivet pin connecting the plates, and a “roller” which rolls on the rivet (so between the plates). The chain is made of hard steel, but this does not save it from wear with use. The chain makes thousands of revolutions every day; and every time it moves, it works on the chainrings (in the front) and on the sprockets (at the back), wearing them as well. It is a very slow process, but it is relentless.

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