Another thing
@dbx71 :
There's the brilliant "ACTI" telemetry tool for AC.
If takes a few fps if you're cpu limited (mostly not a problem at all when practicing alone or with only a few cars! Just disable it in content manager before a 20+ car race, depending on your cpu).
It records the line, brakes, throttle, steering angle, rpm, shifting, slip angle, camber angle etc etc etc.
The biggest point are the driver inputs and the line though.
No matter how much you slow down a replay and do splitscreen video editing or whatever, you'll never get down to the level of detail of telemetry.
The problem is that the time lies exactly in these details!
If you want, install ACTI and do some hotlaps at Road America with the car of your choice.
It's important to go back to the pits after you did a good lap (teleport is fine) and then drive a few meters out of the pits again to wrap up the stint recording of the good lap.
Then zip me all motec files you have and upload them somewhere (documents/ACTI/.. Somewhere there, at the phone right now).
I'll do a quick analysis for you
It's probably a few general things where you need to change the approach/pattern and then a few single moments.
The single moments aren't important for the next track. Only when you want to nail Road America for the next race there.
But the general things can be taken to all tracks and often all cars too!
Using acti + motec got me from the midfield to the front rows with some cars, if I put in the practice!
And it also showed some interesting things like a grippier mx-5 being slower through tight corners, since you don't want to go for max cornering speed. You need to very slightly drift the rear to have a tighter turning radius while already accelerating.
You can't see these things on replays, YouTube etc.