It is important to correctly setup the steering wheel.
1 ) In the steering wheel profiler, disable the centering spring and damping, or at least let the software override them.
2 ) Take note of the rotation ( the suggested value is 180 ).
3 ) In World Racing Series -> Settings -> Input -> Calibration, calibrate the steering wheel rotating it from lock to lock, and then leave it perfectly centered before pressing "Ok".
4 ) Click on the right of Controls -> Steer and steer LEFT to assign the control.
5 ) Under Advanced -> Steer, set deadzone to 0, linearity to 100 and leave smooth unchecked.
6 ) Enable force feedback and set strength to 100%, deadzone to 0% and linearity to 100%
7 ) Enable wheel rotation and set it directly or use the wizard. In both cases the value should match the rotation set in the profiler.
8 ) If you are experiencing vibration on straights, please try increasing force feedback deadzone in steps of 5. This shouldn't be needed on the Logitech G25 and G27.
9 ) If you feel the force in the center is a bit weak, you can try lowering the force feedback linearity.
This is how the FF curve looks like at 0 ( top ) and 100 ( bottom ) linearity: