Friction coefficients between different wheel/tire materials and concrete

You can find good background information on friction here.

Here is an excellent discussion on friction coefficients, plus a comprehensive table of friction coefficients.

Figure 1: Static vs dynamic friction

Friction coefficients of thermoplastics against steel.

Friction coefficients for common material combinations.

After reviewing the links referenced above you should be able to conclude the friction coefficient for typical plastics on concrete is roughly half the value for dry and clean rubber on concrete, as summarized in the following table.

Friction Coefficient Summary Table:

Material Combination	Static Friction Coefficient
soft rubber on dry concrete	0.85
hard rubber on dry concrete	0.6
soft plastic on dry concrete	0.6
hard plastic on dry concrete	0.3
soft rubber on dry wood	0.95
hard rubber on dry wood	0.7
soft plastic on dry wood	0.7
hard plastic on dry wood	0.4