Ceramic wheel bearings were investigated. Literature from companies that specialized in ceramic bearings was ignored. They have a big financial stake in what they say. This could make the recommendations suspect. Engineering data was reviewed from big established bearing companies such as Timkin, Toyo, GMN, NSK, NTN, and others. They often sold ceramic and many other bearing types. Their guidance would be more impartial, is my hope.
Wheel bearings are sealed low speed deep groove radial ball type. Lifespan is not an issue with a seldom used race bike. There was very little, if any, advantage for ceramic bearings in that use based on the literature.
Then, some investigation was done on the top of the line performance bikes from major manufacturers. The four cylinder BMW1000SS would be a example. All appear to use conventional steel bearings. So, I decided to use steel bearings, too.
The Tiger 800 bearings removed are Japanese NSK 6204DU and they are replaced with Polish NSK 63030DU with the same width and outer diameter. The inner diameter is smaller to match the Triumph Bonneville axle.