Rigging and taking Collisions in 4.7.6 car mesh

Every time we start the simulation the collision mesh will snap to origin. We have a simple car rig with a major bone in origin and 4 bones in each tire axis. Any help will be appreciated. Thanks.

here is a tutorial, i made some cars and all work fine, main request on preparing model in any 3d program is you need use minimum 5 bones with this axis(on all 4 wheels and root ) ---- x - front, y - left and z - up, other bones can be directed what you like