After watching carefuly what happens with my car (FWD, so geometry is supposed to have a scrub radius close from zero), I noticed:
- I do not feel most bumps through the steering wheel. I feel them through acceleration, and if I feel like the wheel is trying to shake my hands, it is in fact the contrary happening: my arms and hands try to shake the wheel because they are pushed by lateral and vertical acceleration on bumpy surfaces. Maybe in iRacing they put a part of lateral acceleration into FFB to simulate this effect.
- I can feel bumps smaller than tyre width through the steering wheel. They impact the tyre on one side only, and it is like scrub radius is not zero anymore. Smaller bumps give a lot more feeling even on cars with zero scrub radius. Maybe that is what is missing here.
- In my car, FFB strength seems to be directly proportional to steering angle. I mean if I turn the wheel 40 degrees it seems to resist two times stronger than when I turn it 20 degrees. I know this is not very logical when you think about caster effect...which is proportional to sin(angle).
There is this document, about steering wheel torque in a nascar car:
http://www.mscsoftware.com/sup ... manHaas_steering_feel.pdf
Look at figure 1. Steering torque is directly proportional to lateral acceleration (which is proportional to steering wheel angle before grip limit).
There is another document from a Renault driving simulator test. They try different laws for steering torque/steering angle dependance, and the default law they use is linear.
http://www.pervasive.jku.at/Te ... vingSimulator_Toffing.pdf
Look at figure 3.
I have the feeling FFB in LFS is not proportional to steering angle, and that is why it is very soft close from center and a lot harder further. Should it be proportional? Is it proportional most of time IRL?
Edit: Finally it makes sense for me...FFB should be directly proportional to steering wheel angle (tyres not sliding).
It comes from rack an pinion mechanism. To explain quick and dirty (I know it is very very simplified):
- Rack displacement is proportional to steering wheel angle.
- wheels angle are in asin(Disp/steeringArmLength)
- trail, hence FFB is in sin(WheelsAngle)
this is directly proportional to SteeringWheelAngle.
Is it the case in LFS? For me it does not feel proportional, but it may come from the FFB wheel mechanism. IMO it feels like in LFS wheels angle is steering wheel angle divided by steering ratio. In that case...FFB is no more proportional to steering wheel angle.