RF tethering

Mama Jo · May 4, 2009

After informing somone in another thread that my BLVD was RF'ing and tethered to the same seat rather than the seat in front of it, I was scolded by several people because apparently that's a no-no.

I figured it would be a good idea to start a new thread on this because I asked a couple questions that didn't get answered and assume people probably never saw them... and this might help someone else as well.

So to address several questions/issues brought up in the other thread:

1. The front seat has airbag sensors. I was informed that tethering to the track or frame of the seat would not interfere with the airbag sensors, however, the only metal parts of the seat that could possibly be tethered to have airbag sensor wires running along and attached to them. Also, there is nothing in the middle between the driver and passenger seat that is bolted to the floor that could be tethered to. And the seatbelts are attached to the seat, not to the floor, so they can't be used for a tether anchor either.

2. The seat that the BLVD is sitting in is fairly deep. And due to the more upright angle of install, the tether strap does go straight down when being attached to the same seat. However, the D ring strap is coming out from underneath the seat.

So am I to assume that I can't tether this seat RF'ing?? I'm still looking for info as to why I can't tether to the same seat, because from my non-expert perspective, it seems a better option than not tethering at all...

joolsplus3 · May 4, 2009

The sensors for the airbag aren't down there in the solid metal part of the leg or seat track. They are weight sensors somewhere in the seat, so tethering to the very bottom of the seat is not going to add 'weight' to the seat that would cause the airbag to think that a light child was in it and deactivate it (as having a seat firmly braced against the upholstered seatback may make a full sized passenger appear to weigh less and thus deactivate the airbag).
Britax did used to not say that tethering to the same seat was a no-no, but then they retested and decided that it performs better when the tether is more toward the front of the vehicle rather than straight down or under. I am inclined to trust them...

Defrost · May 4, 2009

joolsplus3 said:
Britax did used to not say that tethering to the same seat was a no-no, but then they retested and decided that it performs better when the tether is more toward the front of the vehicle rather than straight down or under. I am inclined to trust them...

Yes, and it was my understanding that it tested better untethered than tethered straight down/under. Am I remembering that correctly, anyone know?

Mama Jo · May 4, 2009

joolsplus3 said:
The sensors for the airbag aren't down there in the solid metal part of the leg or seat track. They are weight sensors somewhere in the seat, so tethering to the very bottom of the seat is not going to add 'weight' to the seat that would cause the airbag to think that a light child was in it and deactivate it (as having a seat firmly braced against the upholstered seatback may make a full sized passenger appear to weigh less and thus deactivate the airbag).
Britax did used to not say that tethering to the same seat was a no-no, but then they retested and decided that it performs better when the tether is more toward the front of the vehicle rather than straight down or under. I am inclined to trust them...

I'm just afraid that even though the sensors aren't there, the tether strap would interfere with the wires themselves, which could then affect the airbag deployment. What if the wire was severed or something, which turned off the sensors, and the airbag never deployed because it didn't "sense" any weight in the seat??

Defrost said:
Yes, and it was my understanding that it tested better untethered than tethered straight down/under. Am I remembering that correctly, anyone know?

That would be good to know... because I'll be honest, I haven't unhooked the tether from where I had it originally...

Pixels · May 4, 2009

It sounds like you might be confusing the wires for the weight/airbag sensors with the sensors themselves. The wires on the leg of the seat are not the actual sensors, they just carry the information to the computer. The only worry that I would have about wrapping the D-ring there is that over time it might break the insulation on the wire. How firmly are the wires attached to the leg? Can you slip the D-ring between the leg and the wire?

ETA: crosspost

Pixels · May 4, 2009

Mama Jo said:
I'm just afraid that even though the sensors aren't there, the tether strap would interfere with the wires themselves, which could then affect the airbag deployment. What if the wire was severed or something, which turned off the sensors, and the airbag never deployed because it didn't "sense" any weight in the seat??

I don't think you need to worry about the wire being severed in the course of a crash, only about it being damaged before hand. During a crash, the first thing that happens is everything moves forward. This is the phase when the airbags go off. At this point, the tether is even more slack than it was before the crash. During the rebound phase of the crash, everything sort of bounces back. This is when the RFing tether gets tight, and does its job. IF the tightness of the Dring was going to sever the wire, this is when it would happen--but the airbags already deployed, so it doesn't matter.

joolsplus3 · May 4, 2009

I've never seen wires down in the tetherable areas...maybe I need to see a picture of your car to understand?

Mama Jo · May 4, 2009

pixels99 said:
I don't think you need to worry about the wire being severed in the course of a crash, only about it being damaged before hand. During a crash, the first thing that happens is everything moves forward. This is the phase when the airbags go off. At this point, the tether is even more slack than it was before the crash. During the rebound phase of the crash, everything sort of bounces back. This is when the RFing tether gets tight, and does its job. IF the tightness of the Dring was going to sever the wire, this is when it would happen--but the airbags already deployed, so it doesn't matter.

See... this is why I need you guys! I dropped out of Physics in high school! LOL

I'll have to mess with it again to see if I could the strap in between the wires and the metal frame. I was just freaked about the strap making any contact with the wires at all. I figure they put them where they put them for a reason, and I didn't want to mess with it!! And something as potentially sensitive as airbag sensors/airbag sensor wires make me nervous!

Pixels · May 4, 2009

Yeah, they put them where the put them for a reason, but it was probably convenience and aesthetics, not function. The wires just carry the signal, they don't do the work of sensing. Moving the wire out of your way is the equivalent of moving the wire on a lamp. Sure, at first you put it along the baseboard, but now that doesn't work because you want to put a piece of furniture there, so you move the wire. It doesn't interfere with the wire's ability to function.

Mama Jo · May 4, 2009

I checked my vehicle over my lunch break, and realized there are no wires under the driver's seat - only under the passenger seat. I have the FN installed driver's side, and the BLVD installed passenger side. I think I'll just switch them tonight when I get home.... Because switching carseats around 4 times this weekend already just wasn't enough for me. lol

joolsplus3 · May 4, 2009

Heh. And I'm not sure there's any weight sensors in the driver's seat, since presumably the driver is adult-sized...

snowbird25ca · May 4, 2009

joolsplus3 said:
Heh. And I'm not sure there's any weight sensors in the driver's seat, since presumably the driver is adult-sized...

Which brings a good question - does that mean it's ok to brace against drivers seats even in vehicles that say not to brace because it can affect the passenger airbag sensor? Driver airbags deploy no matter what...

Back on topic, if forced to choose between not tethering or tethering straight down or slightly back, I'd not tether. The seat performs perfectly fine without a rf'ing tether. :thumbsup:

Mama Jo · May 5, 2009

snowbird25ca said:
Which brings a good question - does that mean it's ok to brace against drivers seats even in vehicles that say not to brace because it can affect the passenger airbag sensor? Driver airbags deploy no matter what...

I was kind of wondering the same thing when I discovered the lack of wires... if there are really no sensors at all, it would make sense that it should be ok... :shrug-shoulders: But just because something makes sense to me doesn't mean it's right... it made sense to me that it should be ok to tether to the same seat (And although I've switched the seats around so it's tethered forward, I'd still be interested in seeing if anyone has any hard data as to why or how the seats did not perform as well... )

An Aurora · May 5, 2009

I'm standing by what I said in the other thread--use the d ring, wrap it around the leg or seat track, and you're not in danger of interfering with the air bag sensors. Especially if you install it on the driver's side where there are no sensors

joolsplus3 · May 5, 2009

Mama Jo said:
I was kind of wondering the same thing when I discovered the lack of wires... if there are really no sensors at all, it would make sense that it should be ok... :shrug-shoulders: But just because something makes sense to me doesn't mean it's right... it made sense to me that it should be ok to tether to the same seat (And although I've switched the seats around so it's tethered forward, I'd still be interested in seeing if anyone has any hard data as to why or how the seats did not perform as well... )

It's a Britax thing... there's an article referring to a study in the LATCH manual that it's not actually bad to tether to the same seat...they used to allow it, then they started saying no (that was after someone asked on another board if you could wrap it down under then up the seatback to the top tether on the back of the seatback of a van, so I thought THAT must be bad in some way...), but they claimed it still tested better when the tether is more forward, no matter how little sense it makes

RF tethering

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