Narrow-Wide Rings Explained
Don’t be surprised if your next bike has but a single derailleur to handle all shifting duties. Single chainring drivetrains are gaining more adherents by the day thanks to a simple chainring innovation, the narrow-wide ring, and advances in rear derailleur tech. For years people have experimented with single ring setups with varying levels of success, using all manner of purpose built and hacked guides to keep the chain from throwing. Today with the help of narrow-wide chainrings, clutch rear derailleurs and wide-range cassettes, the single ring setup functions and makes more sense than ever before.
Bicycle chains consist of alternating pairs of inner and outer links, and narrow-wide rings take advantage of the slight difference in the space between the links to form a more secure connection with the chain than a standard ring. Not terribly unlike skip-tooth rings of a century ago that had miniature teeth for the inner chain links, modern narrow-wide rings have teeth that alternate between narrow and wide, interfacing with the inner and outer links to help prevent the chain from moving excessively while engaged, and in turn preventing a thrown chain. Combined with a clutch rear derailleur—essentially a mechanism that helps to minimize forward rotation of the derailleur body to keep the bottom of the chain wrap taut—a narrow-wide, single ring setup can reliably keep the chain on throughout the entire gear range.
With wide-range cassettes (ex. 11-36) readily available, and supplemental 40-tooth+ large cassette cogs available aftermarket, a single front chainring can provide almost as much gear range as a double or even triple chainring setup has in the past, with the simplicity of one fewer shifter and derailleur. In addition to that simplicity, with all gear changes happening along the cassette there are no redundant or out of order gear combinations as with multiple front rings.
There will be a place for multiple front rings for the foreseeable future—touring, road racing, bikepacking, epic mountain riding—but as clutch rear derailleurs and narrow-wide rings continue to come to market, expect to see more single ring setups making an appearance.