A brief description of bearings and the lowdown on if you should care what material they're made out of.
Without bearings, none of us would be going anywhere. Rolling bearings consist of a circular arrangement of balls or rollers, encased between two concentric rings (called races). One of the races is typically fixed and the other rotates with a moving part such as a wheel or a crankset. The best bearings operate with minimal friction and are able to withstand dirt and abuse. Most high-quality steel rolling bearings do this job very well, but those seeking a small improvement in rolling efficiency or who live in harsh environments may be drawn to bearings that incorporate ceramic materials.
To better understand ceramic bearings, we checked in with an expert at Chris King Precision Components to learn the pros and cons. Chris King is best known for its hubs and headsets, and the company manufactures its own bearings—both steel and ceramic. According to Erik Drews, engineering manager at Chris King, ceramic bearings can be faster than steel bearings but not necessarily because they can be made “smoother.”
“The common pitch for ceramic bearings is that they reduce drag. This is true, but not in the way most people think,” Drews says. “This has little to do with the rolling efficiency of the material, instead it is because it is a non-galling (a phenomenon in which sliding surfaces bond together) material. This characteristic allows us to run far less grease in the bearings, which greatly reduces drag.”
Drews goes on to explain that most of the bearings used in the bike industry are actually hybrid ceramic bearings—as opposed to full ceramic bearings, which tend to be fragile. However, there is a big variance in quality and lifespan among hybrid bearings. “Because ceramic balls are so hard and smooth, the steel race needs to be very hard as well. Otherwise, the ball will wear the race very quickly and ruin the bearing. To counteract this, many companies plate or coat the bearing races in various materials. While this works in the short term, it is not long lasting, and once one little hole is made, the ball will tear through and destroy the bearing,” Drews says.
Another benefit of ceramic bearings is that they resist scratching, and they wear better and longer than a typical stainless-steel bearing because they are made from such hard materials. They are also better suited to harsh environments (Dubai 70.3 anyone?).
Ceramic bearings, however, do cost several times more than steel. A standard Shimano Dura Ace bottom bracket costs about $40, while a ceramic bottom bracket will run between $200 and $500, depending on the manufacturer. Some wheel manufacturers oppose the use of ceramic bearings altogether, simply stating that the added expense is not worth the small performance benefit. With that said, a brand like Ceramic Speed—the most well-known manufacturer of ceramic bearings in the bike industry—claims a 9-watt power savings for a bike completely outfitted with ceramic bearings versus a bike with steel bearings. Considering that this conversion will easily cost over $1,000, a full ceramic changeover should only be considered if everything else is dialed in or your harsh conditions warrant it.