The easiest way to ensure that your shifting is the best it can be and prevent unnecessary wear on the rest of your drivetrain is ensuring that your chain is not excessively worn. Park Tool offers the CC-3. 2 which is by far the easiest to use chain wear measuring tool that is so quick to use we should all be embarrassed at how little we check our chain's wear. The CC-3. 2 is a go/no-go gauge that accurately indicates when chain wear reaches 0. 5 and 0. 75-percent, the points where most manufacturers suggest replacement. Simply put the end of the chain checker in the chain and see if you can place the permanent measuring marked ends into the chain links. For 1 through 10-speed chains, replace it if the gauge on the 0. 75-percent side fits into the links. For 11 and 12-speed chains, replace when the 0. 5% side fits. The CC-3. 2 will quickly save you from frustration and money.