The advantages of ceramic balls over steel for ball bearings are several: formed of silicon nitride (Si3N4), they are about 30percent lighter than steel equivalents and rounder ( closer to a perfect sphere) for smoother running. They are also harder, so they lose less energy to elastic deformation and last longer with greater resistance to water and dirt ingress and loss of lubricant.
The latest such bearings to land on the RCUK desk arrive courtesy of CK Ceramics, based in France. Our test sample is a Shimano Hollowtech II road-type bottom bracket assembly, which is available in six colours and weighs 88g. There’s a mtb version weighing an additional 3g due to the spacers required and a heavier-duty seal that that required for the road.
Grade 3 silicon nitride balls run in ground and hardened chrome steel races housed in CNC-machined aluminium cups with, for the moment, BSC threads. Italian threaded cups are on their way. SRAM-format bearings are also on offer.
Price for the bottom brackets is £99.99 including insured postage. More when we’ve covered a few miles.