Some of the steering vibrations as the road information are useful signals for the drivers to acquire road conditions. This paper examined the relations of steering vibration and the road information by using a steering simulator. The actual steering vibration and random excitations were used for this study. It was investigated which frequency components of the actual steering vibration were necessary as the road information. Furthermore, the road information and solid feel of the steering system were investigated by changing the spectrum of balance and the vibration of the frequency of random excitations. Drivers recognized the frequency under about 4 Hz as unnecessary vibration of steering pull, and the frequency over 100 Hz as unnecessary vibration of itch feeling. When the steering amplitude of vibration was in a relation of 10 dB/dec. for a frequency, the drivers recognized the road information wealthily and steering stiffness.
