How to use a Park Tool CC-3 Chain Checker
The following information was derived from the Park Tool Company instruction Manuals
A worn bicycle chain shifts poorly and wears sprockets at an accelerated rate. The CC-3 is a "go / no-go" gauge designed to accurately indicate when a bicycle or indoor cycle chain reaches .75% and 1% wear, the points at which most manufacturers suggest replacement (contact your manufacturer for more specific data). The Park Tool Company CC-3 Chain Checker is made from precision, laser cut steel.
One side of the Park Tool Company CC-3 is used to check for chain wear at the .75% level; the other side is used to check for bike chain wear at the 1% level. Select the correct side and lower the Park Tool Company CC-3 onto the chain. If guage tip fits completely into the chain link (Figure 1), the cycle chain is worn and should be replaced. If guage tip does not fit into link (Figure 2), the indoor cycle or bicycle chain is not worn enough to need replacement.