Jimmy:
I still don't get it.
Seems like the car frames are essentially the same as when built, circa 1880. 053 and others are sheathed both top and on bottom of the frame, so it is not like the wheels can tuck up between the longitudinal sills ala 3000-series boxcars.
I know the 1939-modernized cars got a massive cast piece with rollers that tracked on a short radiused piece of steel to help stabilize the car. But no other part of the truck seems to have changed save the wheels.
Smaller wheels would lower the car, including the drawbar, and move the steps closer to the ground. Smaller wheels = more revolutions over a given distance which seems to me like more wear. Perhaps a lower car resulted in a lower center of gravity for faster speeds on winding track?
Keith