From the top of my head from
David Greco interview:
1. Proper simulation for aero components - now the game will compute values for front wing, rear wing and underfloor generated downforce instead of lumping them all together and just moving aero balance front-rear bias and diffuser stalling.
2. Wings setup is now absolute. Whereas before you had 1-1 Monza being different to a 1-1 in Monaco, the scale going to 1-50 enables absolute values so a 1 will be the same across all tracks.
3. Grip loss when sliding/wheelspin is now greater, making for a more realistic handling and hopefully putting and end to cars drifting and being faster in slow speed corners.
3.1 Just to clarify, let's your soft slick tyres have a certain coefficient of grip on dry tarmac. When your tyres go over the grip threshold and break traction, the nasty effects are compounded with the fact that said coefficient drops significantly. Apparently in previous games this drop was very modest so your performance wouldn't be that much affected by sliding.
4. Wheel physics have been reworked and now account for way more inertia - bigger wheels and heavier brakes, mostly. So it's harder to catch a slide if you go over the edge as the wheels will be more resistant to changes in momentum.
5. Grip sensitivity to load is now more realistic. Basically, in real life the greater the load (weight + downforce acting on any given tyre) the greater the grip, but with diminishing increases until it comes a point where the grip starts to dip. The game obviously simulated that, but relatively crudely with only 4 levels of grip vs load. Now we've got 12 points in that curve, so the simulation will be more lifelike.
6. Transmission now actually impacts the speed of your throttle inputs resulting in power output at the wheels. Before it was basically a direct link, you'd increase the throttle and the car would instantly plant more power down. Now the game accounts for that minimal time it actually takes for the engine speed to reach the driven axle.
