backless booster weight ratings

[ecoteat]

What is the difference between a backless booster that's rated for 33+ pounds and one that is for 40+? Would the different seats perform any differently if a 37 pound (43", 5.5 yo) kid was in them?

[MariesMama]

The 40 lb seat has not passed testing for children UNDER 40 lbs.  There is a risk of submarining with children that tiny and booster seats.

[ecoteat]

I understand that, but what exactly is different about one that is rated 40 lbs and one that is rated 30 or 33? Two seats may look and function nearly identically, but be rated differently. How are these (30 pound) seats:

functionally different from these (40 pound) seats?

Isn't their purpose just to make the belt fit better? How do the first set of seats up there do a better job of that for a skinny 37 pound kid than the others?

[chickabiddy]

We can speculate about the differences, but the bottom line is that seats with a 40# lower limit have not been tested for smaller children, and with enough seats that ARE tested down to 30#, I'd pick one of those.

My own speculation, which as stated above is mere speculation, is that seats rated for smaller children ideally have some anti-submarining features built in, like a slightly angled seat.

[chel]

Has anyone found a backless booster that even fit young kids well?

I think it is a moot point between 30-40lbs, as unless the kid has an extremely long torso, most kids that light will need something to adjust the shoulder belt and need either the back part or something else to adjust the shoulder strap.

I'm more then willing to over look a few lbs, but found very few cars that I could use a backless booster until my kid was seven-ish.

[DahliaRW]

The backless harmony literider WITH the adjuster clip might.  But I think a hbb is a better choice for kids that are smaller, and prefer to keep mine in a hbb until they outgrow it.  I might let them switch at 8 or 9 if they still have growing room, however...

[ecoteat]

I think everyone here knows the importance of the appropriate seat at any age, myself included. I'm not shopping for a seat; we already have a good, safe set-up for my kid in our vehicles. This is more of a theoretical question, I guess. Maybe I'll try car-seat.org--they might be able to answer my question.