Adding Collider2D changed physics on race car.How to compensate for mass loss in the back of the car?or do it some other way.

AS YOU CAN SEE THE PIVOT IS IN THE BACK ,DOWN, BUT THE CAR BEHAVES LIKE ITS MORE IN THE MIDDLE,(PUTTING PIVOT TO MIDDLE NOR TO THE TOP HELPS),I TRIED ADDING COUNTER WEIGHT OR NARROW COLLIDERS BUT STILL NOT GOOD. THANKS :)