A few years back, I had an opportunity to go to a Goodyear tire manufacturing facility and spend the day building tires, and it was very illuminating.
To start: Natural and gum rubbers, oils, carbon black and other arcane additives they won't discuss are added to a giant mi machine. Rubber flows out of the bottom of the machine like giant sheets of crepe paper. On another machine the size of my backyard, steel wire is woven into sheets on a rubber ribbon and cut into chunks on a guillotine 10 feet long. Farther along inside the mile-long factory, the wire-bead reinforcements, inner liner, sidewall and tread fabric, steel and tread rubber are all hand-assembled on another machine. The rubber, only slightly less gummy than warm chewing gum, sticks to itself readily. The all-important splice in the tread plies is made by eyeball, and a sloppy job leaves the tire with a vibration that can't be balanced out. From the assembly machine, the green tire is conveyored to a mold, where 350 F, 350-psi steam forces the tire into the tread of the mold, expanding it to its final size and vulcanizing the raw rubber at the same time.