Originally Posted by spunkyruss
I have seen hubs containing balls in retainers. They were on my low-end Specialized Hardrock from the mid-90s. I've repalced them with loose balls.
I can't recall the source of my information (or misinformation as the case may be), but I am under the impression that a race that is packed full of balls will generate more friction than a race that contains one less ball.
The exlplaination was that friction is generated between adjacent balls if they are all touching. As the bearing spins, one side of each ball is rotating towards the upper race and the opposite side of the same ball is rotating towards the lower race. If all of the balls are touching, then then the upward-rotating side of every ball is generating friction against the downward-rotating side of the adjacent ball.
If the bearing doesn't contain enough balls to place adjacent balls in contact with one another then the friction will be reduced.
I could be wrong about all of the whole ball-on-ball friction thing.
The bearing retainers reduce assembly labor time so they are done on low end bikes as a cost saving measure. They add friction, so you are only going to see hubs with bearing retainers on low end bikes wherein performance sacrificing is done in the name of cost saving.