Quote:
Originally Posted by Nine8Six
Favoring one for another; a scientific reasoning should still be an influence factor in your decision (brand/makes aside). If your car never rev pass the range of an F1 car, you might as well be better with a roller long term. The ball bearing type however seems to be the trade off and best of both worlds.
Still today nobody have been able to output centrifugal force data on the shaft itself so hard (near impossible) to say which is better. If it be me I'd stick with what Porsche says 
Roller bearings are a type of bearing that use rolling elements to support loads and reduce friction. As opposed to ball bearings, roller bearings have barrel-shaped rolling elements instead of spherical balls. They are capable of supporting heavier loads than similarly sized ball bearings but cannot handle as high of speeds as ball bearings. |
A far larger factor than RPM is the harmonics of the shaft itself; most IMS retrofits still allow, or even encourage, oil intrusion into the shaft, which can set up strange vibrations as the shaft, now partially full of oil, accelerates under load; none of which is doing the rear bearing any good.