Let's see? I just did the IMSB ceramic retro-fit at 22k miles. I average between 1-2k miles per year. If I need to change the bearing again after 40-50k miles, for me that would mean anytime between 25 to 50 years from now. Hmm... I should be all set for a awhile. By the way, do they allow Porsches in assisted living communities ?

With the music you listen to, no way ......

Rather than start up yet another IMS bearing thread....

I've read through all the arguments and theories in this thread. I'd like to add one more that hasn't been discussed at all.

It's known throughout the ball bearing industry that there's a lot of counterfeiting going on. Cheap bearings are marked with "brand name" markings such as from SKF, Timken, et al. The counterfeiters are very clever at making both the bearings and the packaging look identical to the real thing. The only difference is that the fake counterfeit bearings simply have a short working life.

Porsche uses NSK brand bearings for the IMS bearing. However, NSK experienced a rash of counterfeit bearings in the German market just about covering the time frame of the IMS bearings at issue. Product: Resolving of counterfeit problem | NSK

I wonder whether Porsche got a percentage of counterfeit NSK bearings in from suppliers. IIUC the IMS with bearing already installed is received as a complete subassembly from Porsche's suppliers, so Porsche doesn't directly buy the bearings from NSK. A random scattering of counterfeit NSK bearings would explain the somewhat random failures of IMS bearings. There have been many theories proposed as to why certain cars experience IMS bearing failures and why others survive to a ripe old age. Counterfeit bearings could be one significant reason. Porsche engineers may have correctly designed the engine when genuine bearings are used, but did not anticipate inferior counterfeit bearings entering the supply chain.

Guys like Jake Raby have examined thousands of IMS bearings, but it would be interesting to see if even he could tell a genuine bearing from a fake counterfeit part.

Jake isn't a bearing engineer but Ed is and I'd bet that he has looked at a lot of the failed bearings that were OEM. I've seen his analysis and even his comments on the original bearings specs pointed to a potential problem so even if they were genuine ....

Bearings aren't just polished balls but a complex assembly of races. seals, packaging, initial lubrication, etc. designed and specified for the loads and environment that they will operate in. And, of the products that have been out there the longest, even LN had one of theirs that had to be redesigned specifically for them (which is why you can't buy one off the shelf and assume it is the same). This after it showed too much wear in the first few that were installed and then were pulled for analysis.

I have a theory that the cage or separator on the earlier single row bearings may have been the cause of early failures, and possibly many of the higher mileage failures. I believe that poor lubrication allows excessive vibration of the cage leading to its failure. I think that added lubrication helps dampen the vibration, possibly leading to reduced failure incidents of the cage.