Park Tool Chain wear measurement tool

Chain Checker
A worn bike chain leads to poor shifting performance and can even wear out transmission components, causing more costly problems.

The CC-4.2 chain checker from Park Tool is a built-in gauge that measures chain wear.

The CC-4.2, laser-cut, accurately measures a long section of chain and strategically contacts at three points, allowing for quick and easy determination of when it needs replacement.

The tool works on all chains from 5 to 13 speeds (including SRAM® T-Type chains, SRAM® Flattop™, Shimano® XTR® 12-speed and Campagnolo® Ekar™ 13-speed) or single-speed chains, and is designed to accurately indicate when a chain reaches 0.5%, 0.75%, and 1.0% wear, the points at which most chain manufacturers suggest replacing it.

When to replace the chain?
Single-speed chains: replace the chain at or just before 1.0%
5 to 10-speed chains: replace the chain at or just before 0.75%
11 to 13-speed chains: replace the chain at or just before 0.5%

Many transmission manufacturers have specific recommendations for their components. Always double-check to be sure.