Abstract: The tyre mechanical characteristics of an automobile moving at medium and high speed on different roads were studied to provide the automobile structure design and its improvement with test data. By using the test trailer developed, the relationship between various parameters and their mutual influences were obtained from the road test on different roads for automobile tyre mechanical characteristics. The road test result showed that the test data were in accord with the theory analysis, therefore the trailer can be used for measuring automobile tyre mechanical characteristics. Finally, an idea of improving the trailer was put forward according to the experiment result.