I know why! Your center of mass is too low. Likely lower than the ground if you authored your car with the wheels on the ground in /Maya. Somewhere there’s a COM offset. Raise that up to be more in the middle of the vehicle and you should see that reverse.
update:I just saw 's post. You may want to try if you’re getting unrealistic behavior still.
BTW, looks awesome. Vehicles in UE4 are SO much nicer looking than UE3. I struggled and struggled to get a realistic car in UDK, but finally settle don a unrealistic tank because ANY drift became unmanageable. I really want to get a car in, but haven’t the time! Arg! 