Here is what I did, and it works.
(Blender v2.74, Unreal Engine v4.7.6)
Blender:
Scene->Units->change to Metric and Degrees, Scale 0.01, and make sure the scale of car body and every wheel is one, if not, press control + a to apply.
The origin of the car body is 0,0,0 and every wheel is in each one’s center.
The car body and wheel must all above ground.
The front of your car is +X axis, left is +Y axis, above is +Z axis.
No need to add any armature or bones.
Don’t apply the car’s wheel its location(remain the value correspond to 0,0,0)
When export to unreal, make sure change Version to fbx6.1 ASCII, or the car will be very big in unreal engine, others remain default.
Every car wheel’s parent is car body.
The vertices of car body doesn’t include car wheels, just their parent.
Unreal Engine:
Import the car as skeleton.
Create a vehicle pawn blueprint, and select your car mesh.
The wheel bone name is the name in blender, for me, I type Tire_frontleft in Element0, Tire_frontright in Element1, Tire_rearleft in Element2, Tire_rearright in Element3. Though the document of UE said the order doesn’t matter, I didn’t try.
Next set the pawn class throttle input and steering.
Change the physic asset all four wheel to kinetic, and car body to box or simple convex.
Down to here you should be able to drive your car. And remember to set your game mode default pawn class to your car’s pawn blueprints.
I swap the fbx model in unreal engine tutorial, and it works well.