OK, let's define some terms: Adhesion- two dissimilar substances stick together, i.e. water droplets adhere to your skin. Cohesion-two similar substances stick together, i.e. water molecules stick to water molecules which is why the droplets form to begin with. Cohesive forces form the drops while adhesive forces cause the drops to stick to your skin. OK, so far?
The forces mentioned above are pretty much the same forces and are the same electrostatic forces that hold atoms together or form chemical compounds, i.e. negative attracts positive and vice versus and the magnitude of the attractive force depends upon distance. Actually the square of the distance, like gravity, double the separation and the force is reduced by 1/4th conversely reducing the distance by half increases the force four-fold.
Next solid surfaces, all surfaces contain pits, grooves, cracks, crevasses, hills, and valleys. Think of two sheets of coarse sand paper. To pull one sheet across another requires a lot of force as the hills of one sheet fall into the valleys of the second and have to be dragged up and over. Smooth the surfaces, lower hills and valleys, less up and over, less force. Seems as if really smooth surfaces should slide across each other with little or no force however the reverse is true. Extremely smooth surfaces lock together and become very difficult to move. Think two sheets of very clean glass or two highly polished metal plates.
OK, now back to the beginning. As two surfaces approach each other electrical forces increase with the square of the distance until the attractive increase is sufficient to pull electrons from one atom into another either completely or partially. This complete or partial removal of electrons is a chemical bond.
Now your tires: Polymers are held together by the chemical bonds formed between the monomer and the cross-linker. A massive cohesive network bond over the entire polymer.
Put your polymer tire in contact with a dissimilar surface and hill meets valley on a small scale resulting in small adhesive forces. Over time as the cross-links fail released monomers flow downward (gravity) filling more valleys and crevasses, thus, increasing adhesion. The tire is becoming more and more stuck to the surface it is on.
You can see the same effect with adhesive tapes. The adhesive compound is a liquid with very, very high viscosity (cohesion) which chemically bonds to the tape substrate. Put the tape on a surface and the liquid adhesive flows into the crevasses and valleys of the surface forming bonds with it. Over time there is more flow into more valleys and crevasses, the tape becomes more and more difficult to remove. You can easily see the electrical nature of the bonding by pulling cellophane tape off a surface in a very dark room, once your eyes are adapted. Watch the tape junction and you will see the sparks as electrons return to their parent atoms.
All interactions in the man-sized world are electrical interactions as electrons repel each other and/or attract atomic nuclei of their own or other atoms. Solids are really not as atoms are 99.99999% dead empty space so are the "solids" they make up. Everything is almost entirely empty space. Solidity is an illusion brought about by electron repelling electron prevent closer approach