You guys are correct...1956 was the first year Chevrolet offered 22.5" tubeless tires. It was also the first year for the (6) 3/4" - 16 bolt on 8-3/4" circle Bud Wheels. These wheels were available in many widths and offsets for the 5000 Series and up trucks.
I don't know when or if Chevrolet ever put these 6 lug wheels on the 4000 Series 1-1/2 ton trucks, but if they did it was after 1959.
As a side note, 1957 was the first year Chevrolet used the Cast Spoked Hub which used the Dayton type wheel.
Mike B
