Harness tightening system for car seats

A child car seat can include a seat base and a seat shell. The seat shell can include a seat bottom and a seat back along a front side of the seat shell. Shoulder straps can be provided to assist holding a child in place in the car seat. The shoulder straps can extend through openings in the seat back of the seat shell and can be coupled to a splitter plate positioned along a back side of the seat shell. The splitter plate can include a slot for receiving a tightening strap and a roller or radiused edge positioned adjacent the slot to help the tightening strap slide along the roller or radiused edge when tension is applied to it. The tightening strap can be routed through the slot and under the seat shell and can pass through another slot along the seat bottom to tighten the shoulder straps.