Why is this car so unstable at high speeds? Anything over 300 kph and it starts sliding like it's on ice, even with RS tyres. The Veyron mission at Le Mans was almost impossible for me. The car just starts veering left and right, and sliding around. It's crazy. Surely someone else has the same issue?
In that mission you have no downforce. When you draft someone, the Veyron is being pulled forward by a vacuum. There's less air in that space, and the car body's friction with surrounding air is what causes downforce. The closer you get, the less downforce, and thus less (or in this case, zero) grip you have.
For a similar yet opposite phenomenon, look up Nikki Lauda's run withe the Brabham BT46B. Lauda could generate more grip by revving the engine. When a crash fouled the track with oil, everyone slowed down in that area...except Lauda. He floored it instead, which spun up the car's cooling/sucker fan and offered him the required grip.
We don't have that luxury in the Veyron, so when drafting minute inputs are needed. I won this mission by setting the controls to steer with the d pad.
I just pressed it briefly when I needed to guide the car. Til then I had the same problem you do. Once I switch to using the D pad, I golded the mission immediately.
By contrast, the St Croix Circuit Experience shows you how well the Veyron can hold the road at speed when there is no drafting involved.
The bottom line is that you'll need to adapt your assists and control style to match the current situation, and that goes for the entire game.