The two common surfaces that typically have the largest friction coefficients are:
Rubber on dry concrete: The friction coefficient between rubber and dry concrete is relatively high. This is why rubber tires provide good traction on dry roads, allowing vehicles to maintain control and prevent slipping.
Rough surfaces: When two rough surfaces come into contact, such as rough wood on rough wood or rough paper on rough paper, the friction coefficient tends to be higher compared to smoother surfaces. The irregularities and interlocking of the rough surfaces increase the frictional forces between them.
It's worth noting that friction coefficients can vary depending on factors such as surface conditions, materials, and the presence of lubricants. The values of friction coefficients are typically experimentally determined and can vary within a range for a given pair of surfaces.