how do you measure the rf height?

my 18 mo is in a safe seat, her shoulders are barely at the top slot but it seems like her head is almost at the top. How do you measure this? I really want to keep her in this seat if she still fits, but obviously if she's getting too big I need to get her a new seat.

TIA,

You want to make sure you have at least an inch of hardshell above her head when she is strapped into the seat.

I usually strap a child in, make sure the head is relaxed back (instead of craing forwarrd), and see if there is at least 1" of the plastic shell above the head (I just push the cover padding down instead of stripping the cover out).

And the harness slots, I insert a finger into the slot and gauge against the shoulder to make sure the slot is either at or lower than the shoulder when rf. The fabric can be pulled down with a child sitting in the seat and often can look lower than it actually is.

Take a look at this post:

http://www.car-seat.org/showthread.php?t=30201

It shows you pictures of how to measure that 1" of shell, which can be confusing as some measure perpendicular to the shell while others measure parallel to the ground. It should be measured perpendicular to the shell.

Over here in Sweden the rf seats are considered fine until more than a third of the head is above the seat back. Sounds a little more lax but as far as I can tell it still offers great safety.

For whiplash protection, the rule of thumb is that the top of the ears should not be above the top of the hard shell, or about the center of the head. This rule would be just fine for rear-facing, in a perfect install on a test bench.

When rear-facing, the other consideration is that the child is reclined and in a frontal crash they can ramp toward the front of the vehicle. With a 45 degree recline and a loose install/harness, there can be a risk for the head to go beyond the shell and strike part of the interior, like a pillar. Even that soft head restraint is quite hard at high speeds. If the child is more upright and there is a tight harness and installation, perhaps with a tether in use (on models that permit it), the risks could be much less.

So, most manufacturers are a little conservative and say top of the head at the top of the shell when rear-facing in a convertible. Britax used to say the top of the ears at the top of the shell in some manuals. This was done to promote extended rear-facing. The flip side was that it was very confusing in regard to some other manuals and almost every other convertible seat on the market in the USA.

Aventuredad, with all due respect to the way rear facing seats are outgrown by height in Sweden, the original poster is Canadian, where the 1" rule of seat shell above the child's head for rear facing most definitely applies for Canadian certified (and U.S.) seats. It's important to keep the specific concerns and issues of the particular poster in mind when offering advice, because not only will the poster potentially take it at face value, but so will countless others who only lurk and read threads here.

Jeanum said:

Aventuredad, with all due respect to the way rear facing seats are outgrown by height in Sweden, this is the Canadian forum, where the 1" rule of seat shell above the child's head for rear facing most definitely applies for Canadian certified (and U.S.) seats. It's important to keep the specific concerns and issues of the particular poster in mind when offering advice, because not only will the poster potentially take it at face value, but so will countless others who only lurk and read threads here.

Click to expand...

Technically Canadian and International No offense to Canadians or Internationals, of course!

LOL, good point. I should have said it's the original poster who is Canadian.

Here's an interesting commentary on why we should NOT allow children's heads to go above the top of the seat shell (From the Yahoo group 'cpsplist', the writer is Kathleen Weber, one of the best known and published researchers in the field):

"To "pass" the 213 test, among other things, the target on the side of the
dummy's head (the center of gravity, approximately at the ears) must not
rise above the top of the shell. This is to protect against whiplash injury
from the head swinging over the top of the CR. To keep the target down
during the test, the harness needs to be threaded through slots below
the shoulders and it must be very snug.

If an actual child started out with the ears at the top of the shell, it would be an unusual parent who would tighten the harness enough to keep the center of gravity of the child's head from passing the top of the shell in a severe crash, and the child's shoulders would have to be unusually stiff. Since there will always be some ramping, and the heavier the child, the more ramping will occur, limiting the top of the head to the top of the shell, or a little below, is a good guideline. Other reasons exist as well, such a containing the head to minimize head contact injury or even neck compression."


(Ramping is what it sounds like: the head and body slide up and out of the seatback in a bad crash)

Sweden may have different recommendations because their seats are braced on dashboards (airbags turned off) which can prevent a lot of ramping, or they may have support feet to hold the seat up and the child in place better, but here (US and Canada) we have basically wobbly seats that move down a LOT in a crash, and you really want to be careful to keep your kiddos head contained in the seat shell to prevent whiplash injury or worse.

:thumbsup:

As usual, phenomenally clear Jools. I didn't mean to suggest one should always follow the Swedish guidelines, it was more a comment to add some perspective about what some others do. Apologies if I was unclear about that.


It's correct that the seats here are often mounted against the dashboard, with an extra support "leg", or leaning against the back seat. They are anything but wobbly. Seats move little in an accident (when installed correctly).

I just know where to look to copy and paste the appropriate information . (But...I also have a child pushing the top limits of a Britax rearfacing, and my manual clearly says tops of ears even with the top of the seat--head sticking WAY over the top when rearfacing--, so I really wanted to make sure that was a good choice before I let her keep growing that far...). Better to just get a taller seat and stay within the limits :thumbsup:

Yes since the SS1 is not one to have top of head above or at same level to top of carseat, it's best to stick to the 1" rule as we know it.

What are the chances, if her shoulders are just reaching the top slot, that her head is too high (and she does have a bit of a big head)?
I just had her in it and was trying to guage, based on the post in the link, but I'm not always that spacially savy, I just couldn't tell.
I'll get dh to check it this weekend, but if it seems unlikely based on shoulder height I'll breathe easy for a month or so.

The reason I'm holding off is thinking a fronteir might work for us for the 3yo and pass her ma down to baby cakes. Speaking of which, if anyone has a link to the thread that mentions install issues I'd love to read that, I've heard rumors but I haven't found the thread.