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kinematic wheels problem

Hello everyone.
I modeled a car rigged it by myself in blender and exported it into unreal but when I create bone collisons for wheels and set them up to kinematic car suddenly starts to fly everywhere
Here is the project: https://drive.google.com/open?id=0B_PtUje37D2SejZYMm5pLVJmZEk
Help me if you can D:

P.S. Sorry for my bad english