GROOVED BALL BEARING 13X35X13 stihl 026

can some of the saw rebuilders tell me abought these deep grove ball bearings. are they better than oem .do they last longer. what is the advantage of using them? get em or not get em?

Without looking at it I cannot say for sure, however, a radial aircraft engine. The ones used in most of the WW2 aircraft. They had deep grooved ball bearings on the crank shafts because they could stand a high side load, like a propeller pulling the crankshaft out of the engine.

For a chainsaw these type of bearings would be either overkill for the job, or performance wise cause slightly more parasitic drag that standard ball bearings. I would say due to more surface area being contacted on the race, these bearings would hold up a little longer, but I'm not certain.

The PTO side is proprietary (that is not to rule out that they are made in the aftermarket now -- if you trust those types of sources)
The flywheel side is a 16002 bearing -- can usually be purchased at most bearing houses. I've bought both of these bearings for around $26.00
but it has been a while. Just more information.