The peak braking force produced by six tires was measured on three wetted surfaces at five different wheel lockup rates. It was found that the maximum braking force obtained from passenger car tires operated on wet surfaces can be significantly affected by wheel angular deceleration rate. The maximum difference between two values of peak braking force produced by two different lockup rates on the same tire was 33%. Tires with minimal tread patterns exhibited no sensitivity to changes in lockup rate.