I know that the Infiniti (Nissan) sedans have something like 53:47 weight distribution so that its perfectly at 50:50 when accelerating.
Porsche is at around 40:60. THIS IS WHY THEY UNDERSTEER AT TURN IN!
If you've ever driven a Porsche and drive it like any other car, you'd find that it'll understeer like mad. Why? It's because there's no weight up front! If you have extra grip available to any tyre, you shift the car's weight so that it digs into it.
I found that by trail braking into corners with a Porsche, you can actually dig the fronts in while having the tail slide out from behind. If you're not careful the rear is heavy enough to spin you out before you realize it. (Many mid-engined cars with something like 45:55 have a less exaggerated version of the same problem.)
In a FWD car with 90:10 ( :lol: sorry, it seems like it but it's more like 65:35), the car will still understeer. This is because the reverse situation of the Porsche occures. Now, there's so much weight at the front that the front tyres are overwhelmed by it. Therefore, it's so much easier to slide the front out before the rears lose traction.
50:50 is the compromise for the most well balanced car. What the engineers decides to do after that is up to them. A 50:50 car can be an understeerer or a tail happy drifter. At this point, other things come into consideration.
Also, 99.99% of road cars DO NOT GERERATE DOWNFORCE! Those wings and spoilers are only there to MINIMIZE lift. The overall value of lift is still positive. It's a myth!
Most road cars have such huge passenger compartments and high road clearance that lift is inevitable. They can only work to minimize it.