The Cyclo Tools Chain Wear Indicator isa simple, "go/no-go" gauge used to determine if a bicycle chain is stretched and needs replacing. It is a durable, all-metal tool with two different sides to measure wear at 0.75% and 1.00%.
How to use the Cyclo Chain Wear Indicator
Engage the tool: Turn the tool to the side that measures the desired level of wear (0.75% or 1.00%).
Seat the hook: Rest the curved hook-end of the tool over one of the chain rollers on the upper section of the chain.
Drop the spike: Let the spiked end of the tool drop down toward the chain. Do not push the tool down, as you could get an inaccurate reading.
Read the result:
Good condition: If the spiked end rests on the chain and does not fully drop into the link, the chain is in good condition.
Replacement needed: If the spiked end drops fully between the rollers of the chain, the chain has reached that wear percentage and should be replaced.