1" rule and slumping

Stelvis

New member
This is mostly academic at this point, since he still has plenty of room at the top of the shells in both of his current seats, but I have been wondering about this.

When I first set DS way back in his seat with a straight back, he's a good inch higher in relation to the top of the shell than when I take him out. He curls his pelvis under in the seat and slumps down. Same for the harness straps -- when I sit him in there, he's right even with the #3 slot on the TFP, but then once he slumps, he's about an inch below (I have the straps set to the #2 slot because of this).

So, which position would you measure from? Since he would most likely ramp up in an accident, go with the higher of the two?
 
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safeinthecar

Moderator - CPS Technician
The hip straps are going to keep him from...unslumping? during a crash as long as they are tight, so I'd be comfortable going by head height with him in a comfortable sitting posture.
 

Stelvis

New member
Okay. The hips are definitely tight. I notice it more since he's now potty trained and he was in cloth diapers before..I guess it freed up some room in the crotch for him to come forward. Thanks!
 

Pixels

New member
I use the unslumped height for the top of the head, and the slumped for the shoulders RFing. It's the most conservative way to do it.
 

Stelvis

New member
Pixels said:
I use the unslumped height for the top of the head, and the slumped for the shoulders RFing. It's the most conservative way to do it.

I've been using the slumped height for the shoulders. But an inch of torso could equal a fairly long additional amount of time RF. I'm just wondering what the risk trade-off is there...
 

Pixels

New member
Based on crash test videos I've watched, I have a *personal* two inch rule. Both kids have stuff immediately in front of them to hit their heads on. I'd feel differently if there was nothing there, but in a sedan, I consider a RFing seat outgrown *for my kids* at two inches.

As a tech, I go by what the seat manual says, either one inch or top of the head or something else.
 

Stelvis

New member
Pixels said:
Based on crash test videos I've watched, I have a *personal* two inch rule. Both kids have stuff immediately in front of them to hit their heads on. I'd feel differently if there was nothing there, but in a sedan, I consider a RFing seat outgrown *for my kids* at two inches.

As a tech, I go by what the seat manual says, either one inch or top of the head or something else.

That's a good point about stuff immediately behind them. In both cars the seats are very close to touching the passenger headrest, especially the Radian.
 

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