This paper presents a unified tire model for simulating the generation of forces and moments during combination of cornering and braking or driving. A unified relationship between the nondimension resultant force and moment, and the normalized resultant slip vector, with an arbitary vertical Load distribution over the contact patch, is derived. So that the processing of multi-dimension test data is greatly simplified. Especially, parameters of the combined nondimensional characteristics can be identified from the pure sideslip tests. Some test data obtained from tire force and moment tests, and vehicle braking in a turn tests are presented to assess the quantitative validity of the model.