caster is built in from factory it is heavy but responsive you have to have alot of muscle also keep your self in the seatCould this be excessive caster? Also, is it hard to turn (harder at speed vs parking), or is it heavy in that it is sluggish, or not light and nimble, at speed?
Here is MIRA wind tunnel data on a GT40 that John Horsman gave me:Do you have canards fitted?
Single or double nostril?
What is the rake of the car? Front 1/2 inch lower than rear?
Perhaps it is creating a lot of front downforce
Gyroscopic or caster are the likely culprits, as it is speed dependent. Down force would only decrease your camber (make it more negative, top in) and increase your toe in. I suspect the suspension was designed to become more stable at high speeds, thus the heavy steering.This is probably due to gyroscopic reaction. Not much you can do to change it except reduce the rotational inertia with lighter wheels and tires.