The need to consider automobile dynamic problems, in which the vehicle is subject to longitudinal and lateral forces simultaneously, is outlined. Tethered Testing is proposed as a method for measuring vehicle behaviour under these conditions, and up to the maximum lateral force that can be obtained. The M.I.R.A. tethered testing rig and the associated experimental and data analysis procedures are described. It is shown that the rate of change of steer angle with lateral acceleration, and the rate of change of steer angle with slip angle are suitable quantities for characterising vehicle steady state behaviour, and results are presented in terms of these quantities, to illustrate the effects of combined cornering and traction for front and rear-wheel drive vehicles.