When you slam the door of a car the striker enters a U shaped slot in the frame plate of the latch. Although there is a V shaped lead in to this U it is the intent of the designer that the striker not contact the V or sides of the U during door closing. After closing the round section of the striker pin should be centered vertically in the U shaped slot, at least ideally. As the door moves up and down due to inertial disturbances and body twist (forms of chucking) the sides of the U slot and the striker pin may contact causing a clunking noise. Alternatively, if they are resting in contact differential motion can cause a groaning or squeaking noise. Coatings and exotic lubricants such as Krytox are used to reduce this.
The above pertains to chucking in the up-down direction of a side door. There is also cross car chucking. When a door is closed or slammed the depth that the striker pin enters the U slot of the latch is determined by the mass or moment of inertia of the door and the velocity of the door in combination with an elastomer bumper in the latch (overslam bumper) and compression of the door sealing system. These elastomeric elements compresses to a point that the kinetic energy of the door has been stored or otherwise absorbed. At this position (assuming the slam was sufficient to latch the door closed) the striker pin will be far enough engaged into the U shaped slot that the major mechanical element of the latch (many names - bolt, ratchet, etc.) can freely swing into place without contacting the striker. As the overslam bumper rebounds the striker is brought into contact with this mechanical portion of the latch where it is designed to stay. The striker pin and the hard mechanical element of the latch are held in continuous contact by pressure from the overslam bumper and the door seals. If dynamic loads during vehicle motion force the door inward with enough force to overcome the overslam bumper and door seals (chuck) then the striker temporarily loses contact with the mechanical element of the latch and will make a clunking noise when they come back together. That noise is the primary reason that the movable portion of the latch is usually overmolded with plastic. Sometimes strategies such as anti-chuck bumpers, tapered wedges, or latches that tighten on the striker pin during chucking are employed to resolve chucking problems.
Mark
