Why are FF limits so much higher?

soccer_widow · Jun 29, 2009

This may be a stupid question, but I was thinking the other day and started wondering why there is such a huge difference between the RF and FF limits on some seats. Why would the same seat be able to properly restrain a FF 80 pound child, but only a 35 pound RF child? Is it the physics involved in the crash and the stresses on the seat, or just the fact that these seats haven't been tested for higher weights? Can anyone explain this to me?

Thank you!!

myliljunebugs · Jun 29, 2009

I *think* it has to do with overrotation. When FF'ing the car seat is up against the back of the vehicle seat, when RF'ing it is just open in the back. Lots more movement involved that way. I assume that is why RF'ing seats that go higher have a bar at the base of it that goes to the floor to brace it. I could be all wrong though LOL

joolsplus3 · Jun 29, 2009

RF seats have to try to hold up from downward rotation. It's hard to keep a seat from dumping backward (in the US, we have seats that must be installed with just a lapbelt, we can't add extra features like footprops to keep seats from dumping down, crashing into front seatbacks, and putting huge amounts of force on the shoulders and spine). Forward facing is pretty easy to meet the requirements, by comparison...it's easy to hold bodies simply back in a crash, they learned that trick decades ago when they invented seatbelts

Splash · Jun 29, 2009

Yeah, what Julie said. Also, in a FF seat, you're holding back the whole seat by holding the frame across a relatively high/large area. When RF, you're holding it back by a low/small area and creating a pivot point.
It's like putting a child in a chair and holding the chairback while the kid dances and flails. Now try doing it holding on just to the very bottom of the front legs. It's a lot harder to keep that chair still and upright then.

Why are FF limits so much higher?

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