In this study, the results of a steady-state cornering test using a sport-touring motorcycle and the analysis of those test results are presented. This test was conducted as one activity in our efforts to realize a quantitative development method for motorcycles. The measurement data from this test include measurement results for tire force, tire moment, and tire slip angle that have not been practically addressed in the research of motorcycles, in addition to normal measurement results for velocity, steering angle, steering torque, roll angle, and the like. Up to now research on motorcycle dynamics characteristics has indicated that “there is a strong relationship between the motorcycle dynamics characteristics and the tire slip angle”. However, since it is difficult to take highly precise measurements of the motorcycle's tire slip angle during actual riding, especially when the motorcycle is tilted during cornering, such measurements have been avoided.[ 1 ] Nevertheless, in this research we attempted to measure the tire slip angle and also attempted to investigate in detail the dynamics characteristics and tire characteristics during riding. Up to this point there has not been an adequate investigation conducted under a variety of riding conditions, but it is the aim of this research to show that it is possible to measure the tire slip angle with good accuracy. It is our opinion that this will open a new path to a more detailed investigation of the motorcycle's dynamics characteristics. In addition, we conducted measurements using not only the normal rider's lean angle (lean-with posture), but also measurements in the case where the rider's lean angle was intentionally changed, in order to investigate the effects that a change in the rider's posture has on the variation in the measurement results of the motorcycle's dynamics. Furthermore, we then compared these measurement results to the results obtained from simulations. Additionally, steering index values were calculated from the measurement results. These calculated index values include the stability factors, slip angle factors, and steering torque factors.