How tight should the car seat be installed in my vehicle?

The car seat should not move more than 1 inch (2.5 cm) at the belt path from side to side or front to back. You can test for tightness by grabbing the sides of the seat at the belt path and sliding it side-to-side and front-to-back. If the seat moves less than 1 inch (2.5 cm), it is tight enough.