Rohloff Caliber 2 Chain Wear Indicator

Replacing your chain, before it has stretched so much that your cassette cogs and chainrings are ruined, is the best way to save money on your bike. The gold standard of chain checkers is the Caliber 2. It’s super-simple to use: Hook the right side into a chain link, then push the left side into the chain. If it goes all the way down, the chain is worn. (In the photo, the chain is new.)

The Caliber 2 has two sides. One is for aluminum cogs (and conservative riders), with a wear limit of 0.075 mm for each 25.4 mm chain link (0.3% stretch). The other, for steel cogs, allows a more generous 0.1 mm stretch (0.4%).

The Caliber 2 may look simple, but it relies on precision machining to give reliable measurements. That’s where Rohloff’s quality comes in. There are other, similar tools available, but most are laser-cut and lack the precision required for accurate measurements.

Pro Tip: SRAM flat-top chains have larger rollers than other chains. They cannot be measured with the Caliber 2 (and similar tools).