Vehicle accident avoidance potential is very much dependent on the vehicle braking and cornering performance potential. In the past, much effort has been concentrated on the suspension and braking systems to raise their performance level. However, vehicle braking and cornering performance is also strongly influenced by the braking and cornering force characteristics of the vehicle tires. The study of vehicle tire dynamics has been generally limited by the absence of accurate braking and cornering tire data representative of the vehicle performance range of interest. This absence of tire performance data is particularly true in the nonlinear tire performance range of large cornering slip angles and braking slip. Accident avoidance vehicle performance research requires tire performance data representative of the tire braking and cornering forces generated by the vehicle tires when operating in the regime of large slip angles, large normal load transfers, and high braking slip, even up to locked wheel performance. The study of vehicle stability and accident avoidance through cornering and braking maneuvers requires tire performance data from 0 to 90° slip angle and from 0 to 100 percent slip for braking.

This paper reports the results of an effort by NHTSA to measure the braking and cornering forces of a P185-80R13 tire produced by Goodyear Corporation. Tire force measurements were made at the Tire Research Facility (TIRF) located at Calspan Corporation. Tire force measurements were made on both dry and wet surfaces. Braking force was measured for each slip angle from 0 to 100 percent slip. The tire slip angle was varied over a slip angle range from 0 to 90°.