Once we understand how tyre rubber works, we then need to understand how tyre grip is generated.  
CREDIT: XPB

Grip is defined as the coefficient of friction between the surface of the tyre and the surface of the racetrack. This friction depends on an array of factors including the roughness of the track as well as the type, temperature and therefore behaviour of the tyre rubber. These factors ultimately affect the deformability and viscosity of the tyre rubber which along with the tyre?s hysteresis are key factors in the generation of grip.  
A tyre generates grip via two types of stress mechanisms:

Indentation
Molecular Adhesion

Indentation
This is where the roughness of the road?s surface excites the rubber material. As tyre rubber is viscoelastic, it distorts and adapts to the texture of the road surface as it slides over it. Therefore, as the tread block strikes a bump in the road, it deforms, but due to the hysteresis of rubber it does not immediately return back to its original shape. This asymmetrical deformation of the rubber generates a reaction force which opposes slippage ? in other words it generates a friction force (grip). Michelin. (2001). The Tyre – Grip. [Online]. Available at: http://www.dimnp.unipi.it/guiggiani-m/Michelin_Tire_Grip.pdf (Accessed 02/01/20)

We can visualise indentation by using the spring-damper analogy explained in ?How tyre rubber works?. As the rubber hits a bump, t...