During the training course (which was EXCELLENT!), Sarah referred to a type of installation that she terms, "Rock your shocks". You know the one, the seat is in there so tight that when you tug on the child seat, the whole car shakes. You're so proud of your tight install - nothing's moving that sucker, right?
Well, actually wrong! You don't want that kind of installation. You see, each component in a car seat, be it the harness, or the seat belt/LATCH belt that is securing the seat is designed to absorb some of those violent crash forces. Let's refer to Sir Isaac Newton here and his first law of motion:
Every object in a state of uniform motion tends to remain in that state of motion unless an external force is applied to it.
In a crash, your child's body (and their internal organs) will continue at the speed and direction that your vehicle was traveling in - until something stops them. You don't want all the stopping force transferred directly to your child.
In a crash, you WANT the seat belt or the LATCH belt to stretch in the crash - that stretching absorbs some of those crash forces, keeping them off your child's body. If you've got a "rock your shocks" installation, those belts are already stretched and so the forces will go directly to your child's body. This is not what you want!
So how should we best install our car seat. Well, it should be in there snuggly. When you tug lightly, with your weak hand, at the belt path, it should not move more than 1 inch laterally side to side, front to back. This is a good installation and will ensure that those violent crash forces are absorbed by your child restraint and vehicle restraint system as they are designed to do.
