Added sources and updated by the Pedalwise team

The chain carries drive force from the chainring to the rear cogs. It wears gradually, which shows up as "stretch".

What it's used for

A worn chain meshes poorly, shifts badly and wears the cogs and chainrings faster. Park Tool notes a new cassette costs much more than a new chain, so replacing the chain on time saves money (Park Tool chain wear guide). Park Tool's general replacement points are 0.75% wear for 10 speed or fewer and 0.5% for 11 speed or more, though makers set their own specs (Park Tool).

What to look for

• A chain that matches your drivetrain's speed count. Check your bike's manual or the drivetrain maker's site.
• The right joining part. Park Tool says each connecting rivet is specific to the chain's make and model, and some chains use a master link instead (Park Tool chain replacement).
• The right length. Size the new chain against the old one, unless the old one was wrong (Park Tool).

Using it safely

• Measure wear with a Chain checker rather than guessing.
• Clean and lube the chain regularly. Park Tool notes that on some mid-drive e-bikes the chain does not move when you backpedal, which changes how you clean it (Park Tool e-bike tools).
• After fitting, check for tight links and make sure any rivet sits flush with its neighbors (Park Tool).
• Skipping after a chain change can mean a worn cassette (Park Tool).

Best price we found

• KMC e8 EPT e-bike chain, 8 speed, 122 links, at KMC's own US store: $31.35 on sale (regular $41.80), checked Nov 9, 2026
• KMC e8 EcoProteQ chain, 8 speed, 122 links, at Performance Bicycle: $41.80, checked Nov 9, 2026 (back order)

Both are 8 speed chains. Match the speed count of your drivetrain. Prices change often, and a local shop may match them.

Videos

Guides that use it

• Check and replace a chain
• Clean and lube a chain
• Adjust a rear derailleur

Sources

• When to replace a chain on a bicycle, Park Tool
• Chain replacement: derailleur bikes, Park Tool
• What tools do I need for my e-bike, Park Tool
• KMC USA store: e8 EPT chain $31.35
• Performance Bicycle: KMC e8 EcoProteQ chain $41.80