Why NOT use a RF top tether?

Just to be abundantly clear, I'm not at all asking why I can't go against MFG instructions and tether a RF car seat that doesn't allow it.

I was just wondering... what reasons would any manufacturer have for NOT allowing it on a convertible car seat? Just because they're too cheap to put it through the testing with it? Because they don't want to include RF tether straps? Is there any theoretical or known scenario in which using a rear-facing tether might cause a seat to fail or even reduce its safety? It shouldn't require any modification of the seat. Convertible car seats have to withstand a lot more tension in a FF installation with a tether compared to a RF installation with a tether.

Just sitting here musing. Has anybody ever heard of any adverse affects when RF tethering was used on a seat that didn't allow it (in testing or in real life)? I'm just trying to figure out why RF tether options are SO incredibly limited.

The directional forces are different rear and forward facing. I don't speak enough engineer to explain it. But they're different. I'd be worried about a seat that hasn't been tested breaking in half and breaking the child's back. It's quite possible they WERE tested that way, and failed.

Wendy

Because RF seats are 'safe enough' without them, and installation issues are too complicated. That's my guess. Actually, even non tetherable ones are safer http://www-nrd.nhtsa.dot.gov/pdf/esv/esv19/05-0346-O.pdf So I at least don't have to have a heart attack when I hear about people doing it to their non tetherable seats

Shell strength is part of it. One rep I talked to thought their seat would need to be redesigned in order to handle a RF tether, but as it turns out, it was just fine.

joolsplus3 said:

Because RF seats are 'safe enough' without them, and installation issues are too complicated. That's my guess. Actually, even non tetherable ones are safer http://www-nrd.nhtsa.dot.gov/pdf/esv/esv19/05-0346-O.pdf So I at least don't have to have a heart attack when I hear about people doing it to their non tetherable seats

Click to expand...

That study has several serious flaws that make it meaningless. Among them, the tethered seats were installed much tighter than the non-tethered seats, which could have led to the "positive but small" benefit. The installation angle was achieved solely by means of tension on the tether, without noodles or the use of other techniques to attempt a normally reclined installation. Only one seat allows installation in that way, and that seat is normally overreclined so it's rare that anyone would use the tether that way. Even the study itself says that the decrease in injury severity was "negligible." (paragraph 4 under Discussion)

You can't say that RF tethered seats are safer based on that study.

LISmama810 said:

Shell strength is part of it. One rep I talked to thought their seat would need to be redesigned in order to handle a RF tether, but as it turns out, it was just fine.

Click to expand...

And there's at least one seat that allows RF tethering, but it was breaking just from installation with the tether.

wendytthomas said:

I'd be worried about a seat that hasn't been tested breaking in half and breaking the child's back.

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Oh, I realize 100% that it should not be done with a seat that doesn't allow it. That wasn't my question at all.

I was just wondering whether we had any actual evidence that, were the manufacturers to actually TRY it and test it, that it would have any negative results or whether seats would actually need to be redesigned to make it work.

NOT "Gee, I wonder whether I should use my child as a crash test dummy because I can't think of any good reason not to." I totally understand that the forces are different, and that something like that would need to be tested before putting it in a real-world car on a real-world freeway.

The study is interesting, flaws and all. It's not enough to prove that it's safe, but it does tend to support my hypothesis that the main reason most manufacturers don't want to do it is simply because they don't want to test it. Most seats probably wouldn't need to be redesigned at all.

Pixels said:

That study has several serious flaws that make it meaningless. Among them, the tethered seats were installed much tighter than the non-tethered seats, which could have led to the "positive but small" benefit. The installation angle was achieved solely by means of tension on the tether, without noodles or the use of other techniques to attempt a normally reclined installation. Only one seat allows installation in that way, and that seat is normally overreclined so it's rare that anyone would use the tether that way. Even the study itself says that the decrease in injury severity was "negligible." (paragraph 4 under Discussion)

You can't say that RF tethered seats are safer based on that study.



And there's at least one seat that allows RF tethering, but it was breaking just from installation with the tether.

Click to expand...

The installation angle was achieved solely by means of tension on the tether, without noodles or the use of other techniques to attempt a normally reclined installation. Only one seat allows installation in that way, and that seat is normally overreclined so it's rare that anyone would use the tether that way.

and


And there's at least one seat that allows RF tethering, but it was breaking just from installation with the tether

Which seats? Define 'breaking'?

Why would a tightened tether versus the need to stick noodles and towels under the front seat to get recline be bad in any way?

joolsplus3 said:

The installation angle was achieved solely by means of tension on the tether, without noodles or the use of other techniques to attempt a normally reclined installation. Only one seat allows installation in that way, and that seat is normally overreclined so it's rare that anyone would use the tether that way.

and


And there's at least one seat that allows RF tethering, but it was breaking just from installation with the tether

Which seats? Define 'breaking'?

Why would a tightened tether versus the need to stick noodles and towels under the front seat to get recline be bad in any way?

Click to expand...

For the untethered seats, they used noodle pyramids and installed normally. For the tethered seats, they placed the restraint on the bench without any noodles and without using the "wedge it in to the seat back instead" trick, installing quite upright. After the lap belt was tightened, they then cranked down on the tether to get the seat reclined to 45ish degrees, thus increasing tension on the lap belt and making the overall install much tighter. Not that the increased tension and tighter install are inherently bad, but it's an apples and oranges situation. The tighter install of the tethered seat could easily account for any reduction in injury measures.

There are three seats/brands that currently allow RF tethering. Two of them, Britax and the Coccoro, don't allow such tightening of the tether to adjust the recline angle. The third brand, Radian, does allow using the tether that way but the seat installs so reclined that it's usually not feasible to tighten the tether so much.

Old-style Britax seats used to allow the tether to be used to recline the seat more, but Britax had to rescind that instruction after it was found that doing so caused the recline mechanism of the seat to break. No, it wasn't breaking in half under the child and it was/is acceptable and safe to use a seat thus broken as long as it is rear facing. But it did break a necessary part of the seat and the seat then lost half its use (forward facing). And that was on a seat that was used according to instructions, after the manufacturer approved use of the tether in that manner. Without manufacturer testing and ultimately large-scale real-world use, there is no way of knowing if another seat would similarly break or have a different type of failure if RF tethered.