The December 2018 update to Forza Motorsport 7 adds a totally new force feedback (FFB) system which is completely physically based, allowing the player to feel the road. The force is now calculated using the alignment torque generated at the contact patch of tire and driving surface, combining both mechanical and pneumatic trail to calculate steer torque. As a result, altering the suspension setup results in force feedback changes. For example, increasing caster angle increases the mechanical trail of the contact patch, resulting more steering alignment force in the force feedback.
It’s a cleaner, more simple system than what has come before it, yet results in a far more dynamic and nuanced experience with a wheel, which makes you feel more connected with the car, and the car more connected to the road than ever before. That is, if your wheel is set up properly and if you have a clear understanding of how to use advanced tuning settings in the game.
How you tune your car will also impact your wheel experience. Many players incorrectly assume that FFB systems or settings make a car understeer or oversteer more. This is not possible. Oversteer and understeer happen to the car at physics level and can be tuned by the player through the car’s tuning setup, not through the FFB settings. Force feedback is what you feel through your steering wheel from those physics effects, and is what helps you feel what is going on at a physics level, it does not affect the car’s behavior.
The image below shows what pneumatic (labelled Tire Self Align Torque) and mechanical trail do in the real world, the result of which is what you feel at the wheel. In game, the same thing happens. If you reduce the mechanical trail, the overall alignment torque is reduced, and the “peaky” aspect of the pneumatic trail only will get exposed.