Go to file "handling.meta", search the line "<fSuspensionRaise value="0.000000" />" and modify the value in "0.050000"
and then in the "Vehicles.meta" put in the flags "FLAG_DROP_SUSPENSION_WHEN_STOPPED"

Dont use this modify if the car is high about sospension (jeep ecc), usually u can use this flag when the car is tuned, (with rocket bunny ecc)