Abstract: A method for quantitatively analyzing steer characteristics to acquire steering stability of vehicles/tires. The method divides the steer characteristics into understeer, oversteer, and power-off reaction characteristics, separately analyzes the understeer, oversteer, and power-off reaction characteristics, analyzes the understeer characteristic using a tuning curvature and a turning velocity characteristic in association with a vehicle turning path, analyzes the oversteer characteristic using a slope of a nose angle and a nose-angle time rate in association with a vehicle attitude, analyzes the power-off reaction characteristic using a nose-angle slope, a nose-angle change rate, and a nose-angle change amount, and compares the above-mentioned characteristics with reference data obtained from a Quasi steady-state condition test during which a vehicle driving state is stable, such that it can quantitatively determine the steer characteristics upon receipt of the result of the comparison.