Why are FFB difference ISI car and Non-ISI car? ISI car has unique FFB. Especially Open-wheel is very extraordinary... Why? Aerodynamics? I think that ISI car is very senstive about UNDERSTEER. Non-ISI car such as URD, BES, IFS3 etc.. has ordinary FFB. They are similar to others(AC, GSC, iRacing) Why difference? ISI and Non-ISI. Which is more realistic?