All I can say is I've had quite a few 9" drum cars through the years and I've never had issue with keeping wheel bearings under them. So I have to disagree that somehow the smaller bearings are prone to problems. I've just not seen it. But that said, I also am pretty particular with keeping my rides up too.
All I can go by is my 32 years in the auto recycling business. I can count on one hand the brake hubs with the A2 outer bearings that I sold for spun races, compared with the hundreds of A1 hubs I sold.
