The peak braking coefficient was measured for five tires at six slip rates on three wet surfaces. In addition, a slick tire was tested on dry asphalt in a similar fashion. The difference in braking coefficient for a tire‐pavement combination over the range of slip rate varied from 3.6 to 33.6%. In general, the effect of slip rate was more pronounced with slick tires and low friction surfaces. In cases where statistically significant differences existed on wet surfaces, the highest friction coefficients occurred most often at intermediate slip rates (between 36 and 100%/s), and the lower friction coefficients usually were obtained at both very high and very low slip rates. It is hypothesized that a reduction in the slip rate causes an increase in the peak braking coefficient on a dry surface but increases the probability of partial hydroplaning on a wet surface. The balance between these two conflicting effects causes the peak braking coefficient to be maximum at intermediate slip rates on many wet surfaces.

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