The Park Tool CC-2 Chain Checker is a gauge that measures chain wear from 0 to 1% on single speed and most multi speed chains.

What it's for

A chain gets longer as its pins and rollers wear. Park Tool notes that a worn chain causes poor shifting and, over time, extra wear on the derailleur and rear cogs. Checking wear and replacing the chain on time costs far less than replacing a cassette and chainrings.

How it works

Measuring: insert the tool's two pins into two chain links, lightly press the swing arm gauge, and read the wear percentage in the gauge window

Reading the result: the window shows wear from 0 to 1%

Compatibility

• Fits: most single speed and derailleur chains, including Shimano XTR 12 speed chains
• Does not fit: SRAM Flattop and SRAM T-Type 12 speed chains. Park Tool says those need the CC-4.2
• 5 to 10 speed chains: replace at or just before 0.75%
• 11 and 12 speed chains: replace at or just before 0.5%
• Single speed chains: replace at or just before 1%

Specs

• Measuring range: 0 to 1% wear
• Park Tool item number: CC-2