Use the auto ffb in game....works great for me.
Or check the forms.
Enable the black box in cockpit with the ffb option at the very bottom.
Run a few laps and you will see a yellow auto ffb appear click on it.
Repeat a few times and it will dial it pretty well.
Also on the options home screen . Enable use custom settings per car in the bottom left. As every car is different and it will save your settings per car.