"Leon" wrote in message

I am no engeneer but did your friend explain how smaller bearings equate
to
longer life? It has been my experience that larger bearings tend to last
longer. Perhaps a better quality bearing will last longer than a lessor
quality bearing but I would find it hare to swallow that smaller bearing
last longer than larger bearings.


The larger the bearing, the more load it can handle. However - - - The
larger the diameter, the more travel each ball or roller will make on a
single revolution.

I have two cars that will turn 2,000 RPM at 70 mph. I drive a lot at that
speed every years. I had a rental car that I liked, but at the same speed,
the engine was turning 2500 rpm. After driving it a while I decided I'd not
buy one for myself. Why? I keep cars well over the 100,000 mile mark.
Given that I may drive it 100,000 miles at 70 mph, the crankshaft will have
turned 43,103,000 times more than my present car. Lots of wear on them
bearings.

So, if bearing "X" is 3" diameter it will have a ball travel of 9.42 inches
while a 2" bearing will travel 6.28 inches. At 4,000 rpm, the larger
bearing will cover 3142 feet while there smaller bearing will have gone 2094
feet. Given proper loading, I'd say the smaller would last longer purely
from a friction point. That would also mean proper operating temperatures
and lubrication.

OK, who knows for sure?
Ed