John, I know for sure in some cases the 40-ton or 50-ton capacity of
a box car was strictly a matter of the trucks, and not the car itself.
Wabash had old trucks put under some new box cars and these cars were
rated at 40 tons. So the differences in crossbearers of the B-4 and
B-5 may, or may not, have anything to do with their capacities.

Tim O'Connor

If it means anything, the B-4 was a 40-ton car, and the B-5--which used only the single heavy crossbearer--was a 50-ton car. You would think the application of the bearers would be reversed.
John Golden
Bloomington, IN