There's something wrong on the setup options/default values.
For ex. on the F317 If the default Diff Power setting is 18 and it's set to move by steps of 5, then why is the minimum value 2.5? If you lower the value in game it goes all the way down to 3 and then 2. You can then raise it back up and set it at 17, but not 18.
The default front spring rate is 146, the step size is 7, and the max is 196. So if you raise it all the way and come back down, you can set the spring rate at 147.
Most of the setup options on the car are like this. The result is that if you raise the value as high as it will go, and then bring it back down, the numbers will all be completely different than they were before. See the attached file for the error that is given every time someone goes on track with the F317 in Assetto Corsa's log.txt when the game tries to load the setup and the values don't match what they're supposed to. It is like this for both cars, F312 and F317