Originally Posted by Louis Wambsganss
Tire rubber is not naturally black, it has to be dyed black. Maybe this is leftover from that dying process. I'm not sure. When using the same procedure on the center of the tread (where the surface is already scrubbed), nothing came off. No rubber; no film.
I'm not sure what other evidence would be necessary to simply establish the mere possibility that new tires might have some sort of film.
That stuff is likely the mold release. After a couple dozen tires you can see the mold release build up in the mold, and after a couple hundred the mold goes from clean aluminum to dark brown, almost black. It builds up enough that you can see the change in a new tire.
The rubber we use in our tires is a mix of natural and synthetic. I don't remember which is which, but one of them is a mottled dark green color, and the other is white. The black color is not from being dyed, but from the carbon black that is added. Carbon Black is added for wear resistance.
I would like to make a video on how ires are made, but I'm not allowed to take pictures or film anything.