Originally Posted by
cpb406
Check out this web page.
http://www.bardenbearings.co.uk/index.cfm?articleid=635
Basically it says the load carrying abililty is greater without the retainer but "With the retainer removed from the bearing the balls are no longer spaced apart and can make contact with each other. With the inner ring acting as a sun gear each ball is driven in the same clockwise direction. At the points of contact the balls are travelling in opposing directions leading to friction and wear. Due to the introduction of ball to ball friction the bearing torque is also increased. The use of ceramic balls can provide lower wear levels and reduced bearing friction/torque."
Even if this is theoretically correct, it's still an "angels dancing on the head of a pin" type of argument.
Loose ball hubs, properly lubed and adjusted, have such a small amount of rolling resistance that any "improvement" is almost unmeasurable. Also, properly adjusted hubs show almost no wear of either the cones, races or balls for thousand and thousands of miles. I have a set of older 9-speed Dura Ace loose ball hubs with 45,000 miles on the original cones and races and they are overhauled only every 5000 to 6000 miles. Obviously the "wear and friction" have to be very low.
These are the points that make ceramic bearings a costly extravagance with no demonstrable benefit except to the seller.