The 3,000km Rule
To avoid this accelerated wear of your cassette and chainrings, a general rule of thumb is to replace your bike’s chain every 3,500km. Mind you, this is just a starting point. No two chains will wear at exactly the same rate because no two riders treat their chains the same.
If you’re the type who spins easy gears, meticulously cleans and lubes the chain after every ride, never rides in the rain, and weighs as much as a World Tour climbing specialist, your chain is likely to last longer than 3,5000km. But if you never miss a meal, love to push big gears, ride rain or shine all the time, and don’t even own shop rags, getting 3,5000km out of your chain is going to be a pipe dream.
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These differences in riding style are why it is best to periodically use a chain wear measuring tool to determine the condition of your chain. With the tool in hand, apply pressure to a pedal so the top of the chain is taut, and then place the measuring tool in place and read the results. Indicators on the tool will tell you whether it’s time to replace your chain.
The Ruler Test
You can also measure chain wear using a standard ruler. To do this, you should know that all modern chains have rivets every half-inch and that you will be measuring from one rivet to another one that is 12 inches away.
Start by drawing the chain taut. Align the end of the ruler at the zero-inch mark with the center of a rivet, and then see where the ruler’s 12-inch mark lines up. If it is dead center on a rivet, the chain is in great condition. If the rivet is less than a 1/16 of an inch ahead of the 12 inch mark, then the chain is showing some wear but still has plenty of life left in it. If the rivet is more than 1/16 of an inch ahead of the 12 inch mark, then it is time to replace your bike chain.
