1) Attach gamepad or joystick
2) Go to the Configure->Controls->Controller->Customize manue and hit "show". Verify that your axis reach +100 and -100 values
3) Configure your car turn left / turn right with the according joystick/gamepad axis
4) Get in the car and turn full left / full right
4a) with A / D key
4b) with full excitation of your joystick/gamepad axis
-> In 1st person view you will see that the steering wheel turns less with the joystick/gamepad than when hitting the A/D keys