Park Tool Bicycle Chain Measurement Tool CC-2C

A worn bicycle chain can lead to poor shifting and, over time, can even cause excessive wear to the derailleur and rear cogs, resulting in a much more costly issue. That's why bike component manufacturers recommend replacing the chain at regular wear intervals. Now, you can quickly and accurately assess the wear (or "stretch") of nearly any bike chain with the CC-2 Chain Checker.

Simply insert the Chain Checker’s pins into two links, lightly press the swing arm gauge, and then check the gauge window for an accurate reading. The CC-2 is compatible with most single-speed and derailleur chains*, including Shimano® XTR® 12-speed chains.

To prevent poor shifting and uneven drivetrain wear, manufacturers suggest replacing the chain before the rear cog.
Now, you can swiftly and accurately determine the wear and stretch of any chain with the Park Tool Chain Checker.
Just insert the Chain Checker’s pins into two links, press the swing arm gauge tight, and then check the gauge window for an accurate reading.

CC-2 Features
5-to-10 speed chains: replace chain at or just before 0.75%
11-to-12 speed chains*: replace at or just before 0.5%
Single-speed chains: replace at or just before 1%
Check with manufacturer for specific replacement instructions
*Use the CC-4.2 for SRAM® Flattop™ and SRAM® T-Type 12-speed chains.