Worth it to 'check' IMS bearing during clutch? Clutch recommendations?

[Homeoboxter]

Originally Posted by JFP in PA

The bearing engineer hired by Jake and Charles during their development of the ceramic hybrid bearing basically indicated that a roller bearing offered no advantages over a ball bearing design in this application, and could have limitations, which is why they went with the ceramic ball design rather than a roller design.

I wonder how the engineer came up with this conclusion. Most of the load on the shaft is radial load, and cylindrical bearings are designed specifically for that. So they should last longer in this application.

On the other hand, ceramic bearings are to be used in conditions like high temperature and speed, conditions that are not really true for the IMS. Also, hybrid bearings are not recommended at applications where lubrication is not really good, as the much harder ceramic balls will abrade the steel rings. And lubrication is thought to be not that good inside the IMS.

Another known feature of hybrid bearings is that they withstand shock loads worse than steel bearings, because in the events of shock loads the much harder ceramic balls will make indentations in the steel raceways leading to rapid wear and early failure. Steel is flexible and takes up the shock loads. I wonder if opening valves can be considered as shock load that manifests as repetitive radial impacts on the bearing.

I`m not saying it`s a terrible idea since many cars are ok with it, but there are examples of failed ones too... So are they actually any better than the original dual rows still running in 20 year old cars over 100k miles?