Vehicle PxD6joint

Hi! I am creating a car with PxD6joint, but I have a problem when I am applying torque to the wheels and the car begins to accelerate, the wheels jump up and down, what could be the problem? http://www.youtube.com/watch?v=IvzywJU765s&feature=youtu.be

Probably the collision shapes are off-center with respect to the joint.

Thanks for the answer, but if the speed is not great then all is well, I’ll add a picture PVD can give you is to understand what could be the problem http://www.youtube.com/watch?v=yvLeD_jyIC8&feature=youtu.be

Wheels rotate AddTorgue()