crosschaining

Crosschaining is a term used in bicycle drivetrain design and use to describe a situation where the chain travels at a pronounced angle between the front chainrings and the rear sprockets. It typically occurs when the rider uses the small front chainring with the largest rear cog or the large front chainring with the smallest rear cog, creating a diagonal chainline.

In a properly tuned drivetrain, the chainline is as straight as possible to minimize lateral forces. Extreme front/rear gear combinations pull the chain away from this ideal line, increasing bending and lateral stress on the chain and teeth, and making shifting less smooth.

The consequences of crosschaining include accelerated wear on the chain, cassette, and chainrings, reduced drivetrain efficiency, increased noise, and a higher risk of poor shifts or chain drop. The effect is more pronounced on bikes with narrow chains, tight tolerances, or older components, and it is one of the reasons gear ranges are designed to keep the chain closer to center positions.

Crosschaining is common on multi-gear systems with front and rear derailleurs and is less of a concern on 1x setups, which intentionally minimize front shifting. To avoid crosschaining, riders are advised to use gear combinations that keep the chainline closer to straight, shift the front derailleur before using extreme rear gears, and consider drivetrain configurations (such as 2x or 1x with suitable gearing) that promote a balanced chainline. Proper adjustment and chain length are also important to prevent inadvertent cross-chaining during shifts.