ERF question WWYD

Yeah we have had all kind of theories but who really knows the real truth about those numerical height limits.

QuassEE said:

The standards are dummy based... but there's also a fitment requirement--a child the height/weight given by the seat manufacturer should realistically be able to fit in the seat. If the dummy were smaller than that 40", and the seat only met the rotation allowance.. an inch taller would likely exceed, correct? Therefore a child an inch taller than the dummy may not realistically fit, within the guidelines?

I doubt we'll ever really KNOW.

-Nicole.

Click to expand...

My understanding of the fitment requirement is that it is a standard that is independent to how the seat performs in a dynamic crash test.

Is there a difference in the length of the 2nd gen and 3rd gen dummies?

All of the dummy's weight is going to be in the seat as a whole when it comes to rotation - kids aren't going to be proportioned with the exact same amount of weight in the same areas as the dummies either...

Sorry to sound confused, but in all the discussions I've participated in regarding the rf'ing height limits, this is the very first time I've ever heard speculation over the height of the dummy and how the seat rotates being discussed.

Now all that being said, I do believe there is something about height with a heavier rf'ing child that influences the performance of the seat - but it's too technical for this thread and is more related to structural integrity. My candid 2 cents is that I would have no hesitation using the complete air to 40" but wouldn't use it past 40".

As Nicole said though - we'll never know the exact reason why. Some manufacturers have identical models (on a structural basis) that have 1" while it's neighbor has a 32" limit - it's all about the discussions that have taken place around fitment and the interpretation of the CMVSS 213 requirement that a label clearly state the height and weight ranges of the size of child the seat is designed to fit. I think the 32" is remnants of KISS... no one will ever be able to convince me that a dummy over 32" causes a MA to over-rotate at 30lbs but a dummy with only 1" of hard shell above the head in the RA50 passes at 35lbs. The dummies being used at the higher weight limits have to be a certain height - and I'm guessing that the 35lb dummy is over 32" high...

I'm thinking of fitment as being an opportunity to veto a seat with a bare pass at the dummy height, when a manufacturer tries to make claims about performance above that height. For example, The Hybrid 3 3yo dummy is 37.20". If you only barely pass at that, and claim a 40" child fits in the seat, that's questionable.. While it's a stretch, it's my zany theory And yes, it's just a theory--I have no more information about this than the rest of us here.

I would hope that somebody out there were looking out for us enough to recognize the basic physics--the higher the placement of the weight in the restraint (child's head, in this case) the greater the rotation. In fact--the height/weight distribution scare me more than the raw weights do, when rear-facing... Yet I'd still err on the side of keeping a child rear-facing (and did, with the Radian@45lbs), I think parents should be making an educated decision when doing so contrary to the manufacturers' instructions. We know there's a reason WHY these numbers are different--be it physics or politics...


-N.