The tires changes characteristics of the element constituting change. Stiffness is one of the various characteristics of the tire. Stiffness of the tire is change contact contour. it is known to affect vibration and noise of the vehicle. In this study we conduct to find influence of change stiffness of the tire due to vibration characteristics inside passenger car. For this study we choose tires of available on the market and measure vertical spring rate and lateral spring rate. Also through the real passenger car we find vibration characteristics in the inside of car. In conclusion, vibration energy is reducing with increase in the stiffness and we find the high vibration level of low frequency band in passenger car due to decreasing stiffness.

Among many potential problems associated with passenger cars, the problem regarded as most sensitive and important to the customers is the passenger car’s quietness. In particular, because the trend toward the high-performance passenger cars is increasing, the quietness should be considered reflecting the increasing demand of the customers for the comfort of passenger car ride. Road noises are of low-frequency in the region of 20Hz to 350Hz, generated when the tires are making contacts with the rough road surface while the passenger car is running, in which the noises are resonating within the passenger compartment or with the passenger car suspension. In this research, among the factors related to the road noises, the influencing factors associated with the suspension and the tire design were investigated. In particular, among the tire design factors, the structure and the rubber material were investigated as the influencing factors, and for the investigative purpose, experimental tires were manufactured and road noise evaluations were conducted thorough actual feeling tests. Then the test results and correlations were analyzed using the 6-Sigma statistical method.

The shape of tire footprint is one of the important factor which affects to the performance of tire such as handling, ride and wear. In this study, the effect of the stiffness for tire footprint is investigated. Some tires on the market were selected and tested the vertical stiffness, lateral stiffness by stiffness measuring system. And the contact length, contact width and contact area are tested, too. The contact width and length is reduced by the increase of the tire stiffness. According to the change of the tire stiffness, the leading edge and trailing edge in the footprint have a different shape.