Added sources and updated by the Pedalwise team

A chain tool, sometimes called a chain breaker, is a small press that drives a chain's rivet (pin) out of or into a link. You need one to size a new chain or to remove a chain that has no master link.

What it's used for

Park Tool's chain replacement guide uses a chain tool to drive out a rivet, keeping the tool's pin straight and centered, at a rivet several links away from any existing connecting rivet (Park Tool chain replacement). Chains with a master link are opened and closed with master link pliers instead (Park Tool).

What to look for

• A tool that suits your chain's brand and speed count. Some chains, such as Campagnolo 11 to 13 speed, need a tool with a peening anvil to finish the pin (Park Tool).
• The correct connecting rivet or master link for your chain. Park Tool notes each connecting rivet is specific to the chain's make and model (Park Tool).
• Master link pliers if your chain uses a master link (Park Tool).

Using it safely

• Size the new chain against the old one by lining up the links, unless the old one was the wrong length (Park Tool).
• Drive a connecting rivet until it sits at the same depth as its neighbors, and check that it doesn't stick out (Park Tool).
• After installing, backpedal and flex the chain sideways to free any tight link (Park Tool).
• If the new chain skips, the cassette may be worn (Park Tool). See Cassette.

Guides that use it

• Check and replace a chain
• Clean and lube a chain

Sources

• Chain replacement: derailleur bikes, Park Tool