Swift Physicsbody pinned and joined not working as expected - ios

I'm trying to create a simple car with SKSpriteNode. Physics and everything works great, except for one tiny thing: when my car lands on the ground from a greater distance the body of the car is pushed down and then goes back to its place.
See image:
I want to get the left image, but I get the one on the right.
When it lands on the ground I don't want the body to go into the wheels, I want it to be in a fixed place relative to the wheels or vice-versa.
So here is how I do it:
This is in the car class:
carWheelJoint1 = SKPhysicsJointPin.jointWithBodyA(self.physicsBody!, bodyB: leftWheel.physicsBody!, anchor: leftWheel.position)
carWheelJoint2 = SKPhysicsJointPin.jointWithBodyA(self.physicsBody!, bodyB: rightWheel.physicsBody!, anchor: rightWheel.position)
And this is in the GameScene class:
//Add vehicle
vehicle = DevCar(color: UIColor.blueColor(), size: CGSize(width: 250, height: 50), cameraThreshold: cameraThreshold)
vehicle.position = (CGPoint(x: 0, y: cameraThreshold))
addChild(vehicle)
self.physicsWorld.addJoint(vehicle.carWheelJoint1)
self.physicsWorld.addJoint(vehicle.carWheelJoint2)
I tried using SKPhysicsJointFixed but that did not work either.
Any ideas?
EDIT: this is how the physicsBody is defined:
Here is the car body in the car class.
The car class is an SKSpriteNode and is the body of the car itself, the wheels are its children.
let baseBody = SKPhysicsBody(rectangleOfSize: size)
baseBody.mass = CGFloat(1)
baseBody.dynamic = true
baseBody.affectedByGravity = true
baseBody.friction = 0.2
baseBody.allowsRotation = false
baseBody.density = CGFloat(10)
self.physicsBody = baseBody
And here is the wheel body in the same class:
leftWheel = SKShapeNode(circleOfRadius: wheelSize)
leftWheel.position = CGPoint(x: size.width / -2 + wheelSize, y: size.height / -2 - wheelSize)
rightWheel = SKShapeNode(circleOfRadius: wheelSize)
rightWheel.position = CGPoint(x: size.width / 2 - wheelSize, y: size.height / -2 - wheelSize)
leftWheel.physicsBody = SKPhysicsBody(circleOfRadius: wheelSize)
leftWheel.physicsBody!.mass = CGFloat(0.2)
leftWheel.physicsBody!.dynamic = true
leftWheel.physicsBody!.affectedByGravity = true
leftWheel.physicsBody!.friction = 0.3
rightWheel.physicsBody = SKPhysicsBody(circleOfRadius: wheelSize)
rightWheel.physicsBody!.mass = CGFloat(0.2)
rightWheel.physicsBody!.dynamic = true
rightWheel.physicsBody!.affectedByGravity = true
rightWheel.physicsBody!.friction = 0.3
addChild(leftWheel)
addChild(rightWheel)
EDIT2: Added video
https://www.youtube.com/watch?v=TTwa-t4u4pI

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