Chain wear, often called chain stretch, becomes an issue with comprehensive cycling. The wear is removal of material from the bushings and pins (or half-bushings, in the Sedis style, also, called “bushing-less”, where the bushing is part of the inner plate) instead of elongation of the sideplates.[8] The strain produced by pedaling is insufficient to cause the latter. As the spacing from link to hyperlink on a worn chain is longer compared to the 1⁄2 inch (12.7 mm) specification, those links will not precisely fit the spaces between teeth on the sprockets, leading to increased wear on the sprockets and possibly chain skip upon derailleur drive trains, in which pedaling tension causes the chain to slide up more than the tops of the sprocket teeth and skip to another alignment, that reduces power transfer and makes pedaling uncomfortable.
Since chain wear is strongly frustrated by dirt engaging in the links, the lifetime of a chain depends mostly on how well it really is cleaned (and lubricated) and will not depend on the mechanical load.[6] Therefore, well-groomed chains of heavily used racing bicycles will most likely last longer than a chain on a lightly used city bike that’s cleaned less. Depending on make use of and cleaning, a chain can last only 1 1,000 kilometres (600 miles) (e.g. in cross-country make use of, or all-weather make use of), 3,000 to 5,000 km (2,000 to 3,000 mi) for well-preserved derailleur chains, or more than 6,000 kilometres (4,000 mi) for perfectly groomed high-quality chains, single-gear, or hub-gear chains (preferably with a full cover chain guard).[9][10]
Nickel-plated chain also confers a measure of self-lubrication to its shifting parts as nickel is a relatively non-galling steel.[dubious – discuss]
Chain wear rates are highly variable, therefore replacement by 
calendar is likely premature or continued utilization of a worn chain, damaging to rear sprockets. One method to measure wear is with a ruler or machinist’s agricultural Chain guideline.[11] Another has been a chain wear tool, which typically has a “tooth” around the same size found on a sprocket. They are simply positioned on a chain under light load and record a “go/no-proceed” result-if the tooth drops in all the way, the chain ought to be replaced.
Twenty half-links in a new chain measure 10 in . (254 mm), and replacement is recommended before the old chain procedures 10 1⁄16 inches (256 mm) (0.7% wear).[5] A safer time to replace a chain is when 24 half-links in the outdated chain measure 12 1⁄16 ins (306 mm) (0.5% wear). If the chain offers worn beyond this limit, the trunk sprockets are also more likely to use, in extreme cases followed by leading chainrings. In cases like this, the ‘skipping’ mentioned previously is liable to continue even after the chain is replaced, as one’s teeth of the sprockets could have become unevenly worn (in extreme cases, hook-shaped). Replacing worn sprocket cassettes and chainrings after lacking the chain replacement window is much more expensive than replacing a worn chain.
