A control method of a power steering system for a vehicle having two steered axles, i.e. a first steered axle joining two first wheels, and a second steered axle joining two second wheels, the power steering system comprising: • a first steering device designed to control the steering of at least one of the first wheels, according to a first steering angle (α1), said first steering device comprising: - a mechanical transmission of the movement from a steering wheel of the vehicle to at least one of the first wheels; - a steering assistance device including a first actuator controlled as a function of a parameter related to the steering wheel movement and capable of providing a steering assistance effort to at least one of the first wheels; • a second steering device comprising a second actuator controlled by a controller as a function of a parameter related to the steering wheel movement, and designed to control the steering of at least one of the second wheels, according to a second steering angle (α2) which is set according to a first rule (F1(α1)) depending on the first steering angle (α1), in normal operation of the power steering system; characterized in that the control method comprises: • detecting or estimating whether a steering wheel torque is greater than a predetermined threshold (SWTth); • in case the steering wheel torque is greater than said threshold (SWTth), operating the second steering device in a forced mode by setting the second steering angle (α2) according to a rule (F2, F1) which depends on the first steering angle (α1) and which takes into account at least one different or additional data, in order to cause an offset-steering of said second wheel. • a first steering device designed to control the steering of at least one of the first wheels, according to a first steering angle (α1), said first steering device comprising: - a mechanical transmission of the movement from a steering wheel of the vehicle to at least one of the first wheels; - a steering assistance device including a first actuator controlled as a function of a parameter related to the steering wheel movement and capable of providing a steering assistance effort to at least one of the first wheels; - a mechanical transmission of the movement from a steering wheel of the vehicle to at least one of the first wheels; - a steering assistance device including a first actuator controlled as a function of a parameter related to the steering wheel movement and capable of providing a steering assistance effort to at least one of the first wheels; • a second steering device comprising a second actuator controlled by a controller as a function of a parameter related to the steering wheel movement, and designed to control the steering of at least one of the second wheels, according to a second steering angle (α2) which is set according to a first rule (F1(α1)) depending on the first steering angle (α1), in normal operation of the power steering system; • detecting or estimating whether a steering wheel torque is greater than a predetermined threshold (SWTth); • in case the steering wheel torque is greater than said threshold (SWTth), operating the second steering device in a forced mode by setting the second steering angle (α2) according to a rule (F2, F1) which depends on the first steering angle (α1) and which takes into account at least one different or additional data, in order to cause an offset-steering of said second wheel.