Frictional forces are complicated. They depend not only on the two objects involved but also their conditioning at the moment of the interaction of the two objects. For example, roads made of asphalt become very slippery when freezing rain or snow covers the surface and tires lose their grip when they are worn. Furthermore, even if all these circumstances are fixed, the frictional force also depends on whether an object rolls, slides (kinetic), or is stationary (static) with respect to the other surface.
