Jim Hunter asked:
"Does anyone know in what year ribbed-back freight wheels were outlawed
for interchange? A friend and I were discussing replacement metal
wheels, such as those offered by P2K, and he said that after sometime
in the 1930's all freight car wheels had to be the smooth-back type.
When and why?"

Your friend is incorrect. Cast iron wheels weren't prohibited on new
or newly-rebuilt cars until January 1, 1958, and weren't banned in
interchange until around 1970. There was no distinction made between
ribbed or smooth-back wheels.


Ben Hom