 The coefficient of friction rapidly reaches a maximum value at about 10-20 percent slip, and then declines as the longitudinal slip values increase to 100 percent, which represents a fully locked tire.The maximum coefficient of friction in the 0-100 percent slip range is termed "peak" coefficient of friction, and the lower coefficient value for the fully locked tire is termed "slide" coefficient of friction.The temperature grades, from highest to lowest, are A, B and C. These represent the tire's resistance to the generation of heat at speed.