How often do you need to replace the chain on your bicycle? The answer depends upon several factors, including such things as the weather you ride in, how much you weigh and how well you maintain your bike. A lightweight cyclist who takes good care of their bike might be able to get more than 2,500 miles on a chain, while a Clydesdale who rides in inclement weather and doesn’t ever lubricate their chain might only get 1,000 miles out of it. If you change your chain too early you are throwing money out the window, but if you wait too long to change the chain you will probably have it break at the worst possible time (you know, when you are 30 miles away from home and it’s raining).
The easiest way to see how much your chain has “stretched” (or more correctly, worn) is to use the Park Tool Chain Checker. This simple tool is so easy to use I think you could train a monkey to do it! Just insert the pins that are on the ends of the Chain Checker into two chain links, adjust the gauge arm, and then look at the gauge window to see how worn the chain is. The gauge displays the amount of wear in easy to read increments (.25%, .50%, .75%, and 1.0%). When the gauge tells you the chain is .75% worn it means you need to start paying attention, and when it tells you it is 1.0% worn you need to replace the chain (though I usually replace my chain when it is .75% worn). Park Tool has a short video on how to use this tool (click the link above), but don’t blink since the video is only 33 seconds long (and that is all you really need).
The Park Tool Chain Checker retails for $30 and has a lifetime warranty. The chain checker is machined out of solid aluminum I don’t see how anyone could ever wear it out.