Originally Posted by
Lemond1985
Being the lazy sort, I just wait until the chain starts slipping and skipping before I replace anything. I have so many bikes that I'm constantly switching parts on, that it would be very impractical to keep mileage figures. And besides, isn't the point of replacing a chain so it won't jump out of gear? Why not wait until it actually starts to have problems?
if you wait until a chain starts jumping out of gear, the chain will have worn so much that you will not only have ruined the cassette,, guaranteeing a cassette change, but you will have increased wear on the chainrings as well as the jockey wheels, and having a sloppy drivetrain in general due to wear.
It's all about economics, replacing a chain before a certain amount of wear means less wear on other parts, which will be more expensive than replacing a chain and going 3 or 4 chains on one cassette, not to mention more expensive chainrings.
and then there is the practical side, if you have to change your chain and can't source a cassette, you can't just change the chain.
Coming from a touring background, this is a real factor.
Plus it just makes sense to take care of ones bike in reducing the wear overall on a bike by replacing parts in a timely manner
I hope this helps the OP getting informed reasons on the advantages of keeping track of chain wear.
The 1/16 wear over 12 inches is a typical wear point to keep track of, and like others here, has shown to be a good reference---but how much mileage to get to that wear totally depends on the rider, conditions and mostly how you keep your drivetrain clean.