Thought this might be of some use, its a better/more accurate description of advanced settings thanks to Aaron.
Vibration scale: controls the scale of haptic vibration
FFB scale: controls the scale of combined trail feedback and dynamic forces
Steering sensitivity: Adjusts the DOR with a soft lock
Steering linearity: Adjusts the linearity curve of the steering input, higher makes it more sensitive around center/less sensitive at full lock, lower values make it less sensitive around center/more sensitive at full lock. 50= linear
FFB understeer: this scales the aligning torque from machanical trail, lower values increase its affect, higher values reduce its effects giving a higher feel for understeer (ffb drop off)
FFB minimum force: scales the aligning torque from pneumatic trail (on my setup lower values increase the aligning force from pneumatic trail and higher values decrease it) default value gives unscaled pneumatic trail ffb data
Damper scale: adjust the weight of the wheel
Center spring scale: the spring is the force pulling the steering wheel toward center; that is to say gravity through caster, KPI and scrub radius. This force is overcome at speed through pneumatic and mechanical trail, the causes of align torque. It’s an active force in Forza Motorsport 7 and at racing speed it’s very minimal.
Some extra info
Mechanical trail: this is the distance the center of the wheel trails behind the steering axis and is the main cause of aligning torque
Pneumatic trail: as the tyre deforms and stretches with speed the contact patch of the tyre trails behind the centre of the wheel and gives extra aligning torque