PARK TOOL CC-4 Chain Wear Indicator
The Park Tool CC-4 Chain Wear indicator is a drop-in style gauge that measures bicycle chain wear. The laser cut CC-4 accurately measures a long section of chain and strategically comes in contact with the chain in three places, quickly and easily taking the guesswork out of knowing when chain replacement is necessary. A worn chain will cause poor shifting as well as accelerate drivetrain wear. The tool works on any 5 to 12-speed derailleur chain (including SRAM® AXS®) and is designed to accurately indicate when a chain reaches .5% and .75% wear, the points at which most chain manufacturers suggest replacement.
Chains and cassettes wear together, but you can prolong the life of the more expensive cassette by changing your chain more frequently.