Regarding the McLaren physics, a response from another forum:
JavThe Diff is key to that car, I kind of hate it and feels kind of arcady how when you step on it it picks the front tires off the ground and tightens the turn radius... That's what keeps me from loving that car!
The fast guys exploit that and use gery very low diff values, but I completely hate it so I tend to increse the value quite a lot thus it makes me a lot slower when compared to the top guys wich are indeed the creame of the crop in sim racing.
(...) the car on a high diff value feels like a real car, it pushes but with good technique you can manage it and be fast. On a value lower than 95 it just feels stupid, the damn thing will do a 180 at 60mph going on a straight line, seriously it's like the thing picks the front off the ground and steers by speed differential on the rears whatever steering angle you had in turn in becomes totally irrelevant! (...)
steve 81 from nogripracingA 180 at 60Mph?
I'm thinking [he] has some controller setup issues or something else weird going on.
Also the diff is not the key to the MP-4 at all. Sure it is a part but for me the most important discovery was setting the rake angle a lot steeper.