chainring

A chainring is a circular, toothed gear that forms part of a bicycle’s crankset. It engages the chain to transfer power from the rider to the drivetrain and works with other rings or as a single ring in a 1x setup. Chainrings are mounted on the crank’s spider and are designed to match the chain’s pitch and the crank’s mounting interface.

Most chainrings bolt to a crank spider using a standardized pattern. Common road patterns include a five-bolt, around 130 mm bolt-circle diameter (BCD) setup, while mountain bike configurations often use different BCDs such as 104/64 for triples. Some cranks use direct-mount or proprietary interfaces. In road systems, a larger outer ring paired with a smaller inner ring is typical; modern mountain bikes frequently use 1x configurations with a single chainring plus chain retention features.

Gearing and sizing: The number of teeth on a chainring determines its gearing. A larger ring provides higher top-end speed at a given cadence, while a smaller ring makes pedaling easier. Road systems commonly range from roughly 34 to 52 teeth on the outer ring and 26 to 39 on the inner ring, with compact and standard doubles offering different combinations. Chainrings must match the chain’s pitch (the standard 1/2 inch) and align with the crank’s chainline and derailleur setup.

Materials and design: Chainrings are typically aluminum alloys, though steel or carbon fiber options exist. They may feature ramped or chamfered tooth profiles to aid shifting and prevent chain drops. Narrow-wide tooth profiles are used on some 1x systems to improve chain retention. Proper compatibility with the crank, spider, and front derailleur (if present) is essential for reliable operation. Regular wear assessment is recommended, as worn teeth can cause poor shifting and chain slip.