Guys, I follow the first video MoneyG posted, everything works fine :
I noticed that some issues could occur in Physics Asset if i put a box on the BodyMain instead of the Root. Maybe My previous problem come from here !
I have one more question about this car set up : I feel that the car slide when I go fast an turn. How could I solve that? I looks like the pivot is in the middle of the car not between the two rear wheels like in the real life.