Can you install a car seat too tightly?

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How tight is too tight? Some child passenger safety technicians have contacted Diono and other child restraint manufacturers and asked how tight is too tight to install a car seats. In other words, can the seat belt or LATCH strap be pulled too tight and damage the seat?

Proper installation of most, if not all, child restraints is assured when the restraint moves less than an inch side to side, front to back at the belt path. Checking at the top of the seat is incorrect. After all, the belt in the correct belt path is what will secure the seat during the crash. The belt path takes the brunt of the crash forces during a crash.

Transport Canada verifies that children’s seats meet Canada Motor Vehicle Safety Standards. In the U.S. all car seats must be tested according to National Highway Traffic Safety Administration’s Federal Motor Vehicle Safety Standard’s No. 213 with a lap belt or latch strap with no more than 14 pounds of seat belt tension.  During the crash test, as much as 1,300 pounds of tension is put on the belt. With larger seats, the tension can go up to as much as 2,600 pounds.

So what if a person can double or triple the tension on a seat belt when installing a car seat? Let’s say a big, strong fire-fighter can put about 50 pounds of tension on a belt. A belt path of a child restraint should not crush or deteriorate under that amount of tension. If it does, how will it hold up under the tension in a crash? In a crash test, the force of the child seat, as it comes down on the test bench, far exceeds the weight or load a person can place on a child restraint as they install it.

As for Diono convertible+booster seats, the seat belt or the latch strap should be pulled tight in the correct belt path. It should move less than an inch side to side, front to back at the belt path. However, when installing the top tether strap, pull the webbing just enough to take the slack out of it. It is not necessary to pull the top tether tight when using it for a forward facing or rear facing installation.

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