Steel wheels aren't as robust as one might suppose. The 3.5-ton Michelin floor jack's steel wheels laid down a thin layer of a white, chalk-like substance which I can only suppose was ground steel extracted from the wheels by the heavy weight of the car as the jack rolled forward on the concrete ground while lifting the car.
The substance looked a little like chalk scrawled on a concrete street.
I think next time I'll lay a thin piece of wood or particle board down on the floor for the jack to roll forward on as it lifts the car.
Using a wooden runway probably isn't keeping with the rules of floor jack operation, but I want the steel wheels to last.