Jersey Tom wrote:The rear tires already steer into the turn, every bit as much as the fronts. The difference is, whereas the fronts are steered by driver input.. the rears are steered by the chassis yawing.
In a road vehicle on turn entry you WANT only the fronts to steer. Momentarily when you move the steering angle the fronts are the only tires developing lateral force and thus develop a yaw acceleration which starts the car actually turning. Once the chassis yaws a bit that steers the rear tires, the yaw moment goes away but the car is still rotating, and is now cornering.
On a neutral car, mid corner at max capacity the front AND rear tires are already steered to their max/optimum point. Having additional steering would do nothing. If your car was understeer and the rears had excess grip capacity yea you could technically steer them some more but that will just make the car plow. I'd imagine it would make the car understeer more.. you'd get a bit more lateral acceleration very briefly and then the car would start to yaw OUT of the turn! Not very good for getting the car pointing down a straight.
4WS is good for a low speed or stationary application when you want something that can turn on basically 0 radius (like a forklift) or move purely laterally without really "turning" the car (ultimate for parallel parking!).
But there's no reason for it on a good racecar.
If the 4 tyres are already steering in a corner, then why do alot of the F1 drivers still drift a bit? Wouldn't 4WS effectively give you the same line as the drift, but still allow the application of power? And in your response about the reverse yawing of the chassis, is that not caused by steering correction more than wheel vector?