Bicycle Maintenance 201: How to Change Your Chain

Why change what seems to be a perfectly good chain?

The answer’s actually simple: chains wear out and even break. That wouldn’t be a problem except that “wearing out” means a chain gets longer. Here’s why: 

The anatomy of a chain.

When a chain's new, the spaces between the rollers exactly match the spaces on your chainwheels and cogs (what most call front and rear “gears,” respectively). As the chain wears, the pins connecting the links (hidden inside the rollers) wear down and allow the chain to get slightly longer. This, in turn, grinds away at the teeth on the cogs, which changes the length of their spaces. If you have to install a new chain because the old one broke or a link froze up, the spaces will no longer match. That makes the new chain skip on the cog, and can wear out the chain faster than it should. Worst-case scenario, you may need a new cogset, which costs about three times as much as a new chain (and requires special tools to install). You probably don’t want that.