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."
That's interesting. It seems the primary purpose of their design, which is without a retainer, is to increase the carrying capacity of the bearing, whether axial or radial, and they acknowledge there is increased friction and torque because of the removal of the retainer. But I still say, in regard to reducing friction/torque, that it would greatly depend on the design of the retainer, too, because the typical "tin" retainers found in bicycle bearings don't strike me as being very well engineered for reducing friction. I'd bet the retainers in the Dura Ace and Campy hubs are actually designed to do some good regarding performance, and aren't just there to speed up assembly-