Most important:
Dont drive on a completely green track. The conditions are really bad then and the tires can't bite into the track, which makes it feel icey.
Ok first off wheel settings:
I use Sensitivity of 360° and set it up ingame as well (not vehicle set steering range) in combination with a steering lock in the setup between 16 and 19°
Further settings on the wheel: FF 100, Sho OFF, Abs OFF, Lin OFF, dea OFF, dri 001, For 100, Spr OFF, dpr OFF.
A good example to try is the Chevrolet Camaro GT3 from ISI, which is a bit oversteery due to medium tires and lots of power, but has a good feel. You can also increase the caster in the cars setup a bit, which gives you a bit harder steering wheel.
Most important gert yourself the pedal overlay plugin, which has a yellow FFB bar, which shouldnt go red unless you are hitting curbs hard etc.
http://isiforums.net/f/showthread.php/7546-rF2-Pedal-Overlay-Plugin
For the Carmaro I use a FFB multiplier of 0.85 and 0 FFB smoothing.
So in a short run:
On the wheel everything off except for FF100, For 100 and dri 001 (you can play with it between 0 and 3 it is all without any extra speed from the motor).
Ingame FFB multiplier around 0.8 to 0.85 works for most cars to have no clipping most of the time, the smoothing has to be off. You can set a minimum force in the json file, but it would be only around 1 or 2% for the V2 in combination with the Formula Rim, so I never changed it myself. So for the V2 I dont have to edit any files.
Just a note: FFB varies between the cars. For me the Camaro, GT-R, Nissan 370z GT4 and the Honda BTCC (watch the torque steer) all provide very good FFB. You have also to keep in mind, that rF2 doesn't use any fake effects. Some sims e.g. harden up the steering wheel when you are sliding with the front tires in rF2 the wheel gets lighter like in reality, so at first it is harder to feel the understeer. For me I felt at home after the first few hours and now everything else doesn't even feel close to rF2.