Hi,
I have this problems appearing when I check my Physical asset of my car’s rigging from blender to UE 4 :
I guess it come from my bonnes but I can’t find the way to solved it.
Any help will be welcome 
For a quick solution delete all the bones of your vehicle and just parent all 4 wheel meshes to the car base. Unreal does not require bones with its wheeled vehicle and will take care of it for you. If you are a beginner I recommend that you do not rig a vehicle and export to Unreal since you will face a lot of challenges.
If you would like to continue using your vehicle rig watch this video:
I noticed that the base of both the wheel bones on the left are facing the wrong direction. It is important that you follow the tutorial for proper bone set up for your vehicle. The direction in which the bone are facing is very important.
So your solutions to this are:
1.) Remove the rig and make everything much easier (I highly advise you do this)
2.) Follow the proper rig tutorial and fix your mistakes.
When it comes to solution 2, people face a lot more problems when it comes to the physics of the wheels and it is not recommended that you chose it unless you really know what your doing when it comes to Unreal.
Hope this helps.
Thank you for your Help MoneyG, I adopt the first solution but know I have this artefact:
I try to change My center pivot to center but this is the same matter each time. Any Idea?
Thank you, I changed the approach now, I deleted the bones in Blender like MoneyG said. I imported the car with parented wheels and it seems that is working.
But now the matter is my car seems to be unstable… don’t know why. I make a capture just above !
I noticed some things that might produce errors, so I will just name them and perhaps when you fix them your problems will be taken care of.
- Your root bone isn’t in the center of the car. Notice that the base of the bone is considered as bone position, not the average between base and tip. The tip is actually just a handle to rotate the bone in animations.
- Each of your wheel has a capsule collision, but they need a sphere collision.
- Make sure to set your wheels’ physic type to kinematic. Right now, they are default.
Most of this can be found under https://docs.unrealengine.com/latest/INT/Engine/Physics/Vehicles/VehcileContentCreation/index.html so I would suggest taking a deeper look over there.
Sorry, it’s hard to tell what’s wrong just from the screenshot. Also, how do you attach the sphere collisions when you don’t have any wheel bones.
And please remember that if you don’t have any wheel bones, you won’t be able to use the vehicle animation instance, because it transforms the bones (don’t know if thats important for you)
If you could possibly upload a little clip of what is going on that would certainly speed up the process. At the moment I’m not entirely sure what I am seeing because it could be the result of a various amount of problems.
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.
When you increase the friction scale in your tiretype data, this should also increase the grip and reduce skidding. And the pivot (= the point the car turns around) is actually never between the two rear wheels (ofc only during normal driving, not during a crash)