Do the following:
- Go to cockpit view & place car on a straight
- Record the screen and your controller (or wheel) simultaneously with a phone/camera. Slow-Mo mode, preferably.
- Make sure the on-screen timer (bottom left) or the lap timer is visible in the shot
- Move the controller several times quickly from left to right to left, etc. - and record it
- EDIT: I have realized that for the controller there is a built-in lag to make it smoother. Even at Sensitivity 7 there is quite a delay. So this probably applies only to wheels
- A wheel can even oscillate on its own when rolling backwards or driving forwards at good speed.
- Look at the video and find a point where the controller stick or physical wheel is centered (or almost centered)
- Search for the point shortly after where the displayed wheel is centered (by stepping through single frames in video)
- The difference in displayed times is your total lag
- Total lag = 100-110ms ~ 6 frames
- An independent review of my 2018 Bravia TV has found 33ms = 2 frames for the TV lag - in game mode.
- The red dot steering indicator is always one frame (16ms) behind
- It is possible that the displayed wheel is also a frame behind the actual value used for the physics sim. (hopefully)
- It should be clear from the measuring "setup" that the lag of the camera or of the on-screen timer does not enter the result
- I estimated a lower lag from just looking at how the on-screen wheel reacts. It does not feel slow.