CC-2 Chain Checker To prevent shifting deterioration and premature drive wear, most suppliers recommend replacing the chain at a maximum elongation of 0.5% (11-12 gears), 0.75% (9-10 gears) or 1% (1 gear).
Quickly and accurately determine chain wear with the Park Tool Chain Checker. Simply insert the CC-2 into two chain links and push the measuring angle to the stop. The numbers on the measuring angle now show whether the chain is still within the tolerance range or not.