There is an undocumented feature available within the iRacing app.ini file (Documents\iRacing\app.ini). The feature is called “DriverHeadHorizon.” This setting enables the driver to visually sense a type of roll effect that will be noticed when the car enters or exits banked turns, goes up on curbs, or, in dirt oval cars, can be noticed as the car rolls (tilts) in the turns. Note that this is for fixed monitors and doesn’t really have much of an effect if you’re using a Virtual Reality headset like th Oculus Rift or the HTC Vive.
The setting basically locks your view to the simulated horizon. Your head will stay pretty much vertical and the horizon will stay horizontal as the car banks or tilts to the left or right. You will notice the dashboard and other items in the cockpit moving or tilting to the left or right as your head is locked to the plane of the horizon. The effect is fairly subtle but can make the simulation more immersive. If you have sensitive inner ears or if you are prone to motion sickness, you might not like this adjustment.
This can be particularly useful if you race on dirt ovals. You can get a better sense of how the car is rolling around its center of gravity, or of its roll attitude.
You can enable DriverHeadHorizon by editing the app.ini file. It’s a simple text file that you can edit in Notepad or in the venerable Notepad++. You will find the setting under the [View] section of the file, or just press Ctrl+F and do a Find on DriverHeadHorizon. Note that you have to restart the sim before any changes to the app.ini file can take effect.
DriverHeadHorizon=0.400000 ; Percent to allow the drivers head to stay level with the horizon when the car tilts.
You can adjust the DriverHeadHorizon from 0.000000 to 1.000000. To see the effect it has, I suggest setting it to 1.000000 then tweaking it until it feels right for you. You will probably find somewhere between .35 and .50 to be about right, but set it where it feels most comfortable for you.
DriverHeadHorizon is considered a preference setting, but I think it adds a lot to the simulation, and also helps you become a better driver.