Question Just curious RFing and FFing harness weight limits ..

Pepse

New member
I was thinking today and the harness on the Blvd and Radian (here in canada) are both 30lbs rfing and 65lbs ffing (my Radian is only a 48lber but anyways).

So why can a rfing child only go to 30lbs rfing in the harness but ffing the harness will keep them safe up to 65lbs.

Won't the harness be good to 65lbs rfing as well??
 
ADS

Maedze

New member
It's the over-rotation not the weight the harness can manage. with bigger, heavier child seat swings backward and down too far. can be dangerous. reason why swedish seats have foot prop, so they don't over-rotate.

hope that helps. im sick and not very clever tonight :thumbsdown:
 

snowbird25ca

Moderator - CPST Instructor
I'm just going to expand on what Maedze said. :)

The most important standard from a dynamic crash test perspective, is downward rotation. Measured from vertical, a seat cannot rotate further than 70* downward at any point during the crash sequence. Heavier kids "load" more weight on to the seat causing the seat to rotate further downwards. Rotate too far down, and the seat fails standards.

So basically the rf'ing weight limits are set so that a child can safely use the seat with no risk of over-rotation. The rf'ing limit isn't really indicative of how much weight the harness is physically able to hold, just the maximum weight the seat can hold without over-rotating in a collision. :thumbsup:
 

zeo2ski

Well-known member
So a hypothetical question (I won't go against manf. recommendations, but just wondering in theory...): My child is rear facing in the third row. The CR is tall enough that it goes over the seat back of the 2nd row and rests on it, and it's tethered so it can't rotate downward or upward. What then would the harm be of exceeding the RFing weight limit? I don't plan to use it exceeding the limit, just very curious.
 

Pixels

New member
Well, it wouldn't be able to over-rotate in that case. But we don't know at what point it would fail (and how). I'm guessing that the shell would crack somewhere behind LOs back, or the RFing belt path might not be reinforced enough for those higher loads, and it could rip out. Also, I wonder about spinal compression, because the child's body would be trying to ramp up the seat, but would be resisted by the shoulders mostly and the lap belts to a lesser (I assume) extent. For that matter, depending on how the hip portion is anchored, that could rip out, too.

Of the scenarios I just listed, depending on the seat, I'd guess spinal compression and harness ripping out of the bottom of the shell to be the two most likely scenarios.
 

snowbird25ca

Moderator - CPST Instructor
So a hypothetical question (I won't go against manf. recommendations, but just wondering in theory...): My child is rear facing in the third row. The CR is tall enough that it goes over the seat back of the 2nd row and rests on it, and it's tethered so it can't rotate downward or upward. What then would the harm be of exceeding the RFing weight limit? I don't plan to use it exceeding the limit, just very curious.

Vehicle seats aren't perfectly rigid and are going to have some slight give in a collision as well - if nothing else the upholstery gives quite a bit. As Pixels mentioned there is the risk of stronger loading on the shoulders - I don't know if that would increase the risk of injury or not, but I could see the possibility that it might.

Is it a huge risk? I really don't know. I suspect part of the problem is that the design of rf'ing seats here doesn't allow for a larger crash test dummy to be used during dynamic testing, so they don't really know how heavy a child the seat could support rf'ing.

I could also see the shell developing a crack or something due to the weight of the child loading on to the shell combined with the vehicle seat in front preventing the movement - like the top wouldn't be rotating downwards because of the vehicle seat, but the force on the seat would be trying to make it rotate downwards - it could create a lot of excess force that the seat wasn't designed to handle on the rf'ing belt path/lower portion of the shell if the child was significantly over the weight limit.

I will say though, that I'm not a believer in weighing children to the last ounce. If a kid is 34lbs and young, I'll weigh periodically and when they go over 35 then turn them. If they were older I'd just turn earlier... but seats don't magically fail the second a child goes from 35lbs to 35lbs 3ozs.... Being as we don't know what point they do fail though, it's not something I'd gamble with... Older child, turn pre-emptively. Younger child, turn the second that 35lbs is broke but don't obsessively weigh them every day.
 

lenats31

New member
Without knowing, I am just assumeing that the Swedish seats are made of a different kind of plastic than US and Canadian seats.

Lena
 

shauburg

Active member
Younger child, turn the second that 35lbs is broke but don't obsessively weigh them every day.

But 34.8 lbs doesn't mean that 35 lbs has been broken does it!?!? I still have a few more seconds, don't I?!? :crying::crying: Please give me more time! He's barely over 2 and has a seriously large (off the charts) cute round head! :crying::crying:

(For others reading - don't worry I will do the right thing and flip DS's seat this weekend!)
 

joolsplus3

Admin - CPS Technician
I can't even begin to imagine a car seat shell cracking under the weight of an RF child (maybe in an *extreme* accident...) If they can hold a child in an FF crash, which is MUCH higher stress on the harness and shell at much higher weights, then it's sturdy enough to hold up to an RF crash.
What may happen is that the seat may overrotate, like Trudy says, the front seatbacks aren't rigid like a dashboard or support foot (as most Swedish seats require) , and the stress on the shoulders can cause spinal compression injuries, and a child that large is at more risk of striking something in the vehicle and being injured.

I'm pretty sure it's all about design, not the kind of plastic, that makes Swedish seats RF to higher weights
 

steph

New member
What may happen is that the seat may overrotate, like Trudy says, the front seatbacks aren't rigid like a dashboard or support foot (as most Swedish seats require)

I'm pretty sure it's all about design, not the kind of plastic, that makes Swedish seats RF to higher weights

I could see that as true but like you said not all Swedish seats have a support foot. The Britax Two-way has to be resting agains the seat in front so that would change the theory a bit. Someone told me the two-way is made of the same type of plastic/material as the Regent. It is a very light seat compared to my Marathon.
 

joolsplus3

Admin - CPS Technician
So we're basically guessing :D

I notice that your two way isn't up on a base... I wonder if that has something to do with extra weight being ok? The first high weight us seat was the 'elite' which was basically what you have, with a reverse belt path for RF. It went to a whopping 32 pounds :thumbsup:
 

steph

New member
So we're basically guessing :D

I notice that your two way isn't up on a base... I wonder if that has something to do with extra weight being ok? The first high weight us seat was the 'elite' which was basically what you have, with a reverse belt path for RF. It went to a whopping 32 pounds :thumbsup:

Yeah, its basically the same height as the Marathon with the base, so imagine how much height the base on the MA takes up. It does have a foot prop to recline for rear facing but you can also have the foot prop against the seat front if you want it more upright. But upright that way is like 90 degrees (a little too much - lol).

ETA: also the rear facing tether comes from the bottom of the seat (you can vaguely see a grey box looking thing where the two-way seat back and bottom meet in my pic) versus the top of the seat like the US Britax seats or Radian. It could have something to do with that to.
 

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