I heard that LFS' cars have all the same aerodynamics, I mean for example the LX4 has the same aero of the Formula BMW or others... Is that true? In that case a big part of the stability of a car is done by tires (I think...).
Any answers?

Not true. AFAIK the car body of every car has separate values for longitudinal and lateral drag, as well as a downforce/lift value (though cars do not produce lift yet, due to missing comparable real life values). Aerodynamic components (wings, undertray) also have these values, separately from the car body ones.

Thank you Android! Cleared my doubts!