02/19/2026
Everyone meet the chain checker. The least expensive tool you may ever purchase for your bike. Simple to use and understand, a go/no go type of tool. It can save you hundreds of dollars if used properly. It simply measures chain wear. And .75 mm is the limit the tool measures. So, if the end of the tool fits between the chain rollers, your chain needs to be replaced. What you are looking at is a chain that has stretched about 4mm! The following photos illustrate the wear this drive train has endured.