Bicycle chain wear checker

Estimate bicycle chain elongation from a pin-to-pin measurement and compare it with reference replacement thresholds.

Measure between pin centers with the chain under light tension. Count half-inch pitches, not pairs of inner and outer links.

Measured pin-to-pin length

Number of half-inch pitches

24 pitches = 12 inches or 304.8 mm when new.

Drivetrain

Estimated chain elongation

0.521%

At or above the reference replacement threshold

Unworn span: 12.000 in. Reference threshold: 0.5%.

Measure bicycle chain wear

Chain wear increases the distance between the pins as joints wear. Estimate elongation as measured length ÷ unworn length, minus 1, then multiply by 100. Each pitch is 0.5 inches or 12.7 mm.

A ruler example

Across 24 pitches, a new chain measures 12 inches. A reading of 12 1/16 inches gives approximately 0.521% elongation. Measure several sections and avoid rounding a borderline reading down.

When to replace a chain

Park Tool gives reference limits of 0.5% for 11 and 12 speed chains, 0.75% for 5 to 10 speed chains, and 1% for single-speed chains. Your chain or drivetrain maker may specify a different limit. For 13 speed or unusual drivetrains, follow that maker's instructions.

A ruler cannot assess damaged links or every kind of chain wear. Confirm a borderline result with a suitable chain gauge. A worn chain can also wear out sprockets.

Reference: Park Tool CC-2 instructions.

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