Tether installs for a vehicle without tether restraints

[netarc]

I've moved DD's Roundabout from the Jetta (primary car) to a 92 VW Cabriolet; Radian 65 is now doing duty in the Jetta.

The Roundabout is installed front-facing in the cabby using a lap/shoulder seatbelt, and appears relatively solid, only moves <1" from side-to-side. I'd like to install the rear tether as well, but of course the car's too old to have tether anchor points.

There's probably an attachment point in the trunk through which I can loop the D-ring strap, but in the Britax' instructions it specifically states that the D-ring strap should _only_ be used in rear-facing mode ... so that's my first question, I just find that odd ... why would said strap only be effective in RF-mode, and is it actually dangerous to use the D-strap in FF-mode? Why? :confused:

Second question - I was considering having a tether anchor welded on in the trunk for the carseat ... any potential issues with that?

[southpawboston]

several issues here. first, you can't use the D-ring for FF tethering because, unlike RF tethering, FF tethering is designed to withstand a lot of tension. the D-ring is not designed for that. second, you can't decide to just weld a top tether anchor (for FF) to wherever you feel a good place would be; it has to be a location and attachment method recommended by the car maker. this is not the case with RF tether anchors, since there is no standard that exists for RF tethering. in fact, that's the reason for the D-ring. since there is no standard for RF tether anchor inclusion and placement in vehicles, and few cars have actual RF tether anchors (some GM, volvo cars), britax supplies the D-ring so that you can just pick any old place that you feel is solid to create your own "DIY" RF tether. but since standards exist for FF tethering (and FF tethering is much more critical), the seat is already designed to work with vehicles equipped FF tether anchors, without use of the D-ring.

[Patriot201]

so that's my first question, I just find that odd ... why would said strap only be effective in RF-mode, and is it actually dangerous to use the D-strap in FF-mode? Why?

The physics of a FF seat in a crash are remarkably different from those of a RF seat in a crash. The tether on a RF seat helps keep the seat from cocooning in an accident, but it doesn't have to absorb the same amount of energy as a tether on a FF seat.

[bensmom]

The crash forces are different in a forward facing crash than in a rear facing crash. Definitely don't use the d-ring for FF.
I don't have my current LATCH manual in the house, but it looks like you should be able to retrofit tether anchors. Ask you dealer for Tech Bulletin 69-01-01.

[Defrost]

Second question - I was considering having a tether anchor welded on in the trunk for the carseat ... any potential issues with that?

Having just attempted to install a tether anchor, there's definitely an issue with that. Welding it on won't support the forces of a crash. The tether anchors I was working with are installed with a fairly large, round, flat piece of metal that goes on the other side of the vehicle body where it's mounted. So, when you look at an installed tether anchor and you see a hook attached with a screw, there's more to it than that. Underneath that, where you can't see it, there's that round piece of metal that is holding the hook in place and helping spread the crash forces. That piece HAS to be under the metal - if you just weld an anchor hook to the body, the welding isn't going to be enough.

That's not to say that you absolutely can't install a tether anchor in your truck, of course, just that you can't simply weld a hook down to do it. :)

Oops! You said "trunk," and I read "truck!" Sorry!

[UlrikeDG]

The Cabriolet can have tethers retrofitted. The cost will vary from dealer to dealer (free installation by VW is no longer available). Here's the info for the '80-'93 Cabriolet.

Two tether anchor points on side shelves in cargo area.
Anchor bracket: Use universal anchor bracket provided with child restraint.*
Bolt: N010 240 16
Spacer: 803 019 825B
Washer: N015 401 3
Nut: N011 008 30 s/s to N 01100840

*VW recommends using a "universal anchor" provided by the seat manufacturer. These are no longer common, and I don't think Britax ever provided them. I'm not sure what the best way around that is, but you *do* have a approved spots to install the tethers, so don't worry about trying to rig something.

[papooses]

dangerous to use the D-strap in FF-mode? Why? :confused:

It's basically about eliminating extra steps to keep things simple -- when you can get from here to there without going out of your way, it just makes sense.... The fewer the steps the better: the D ring's sole purpose it merely to be able to use the tether RF, it's just not intended for FF use & why would you want to do something more than necessary when the easy way works great? ;) Reference Ulrike's post when you call your dealership and/or vehicle manufacturer, it shouldn't really be a hassle to get the tether anchor :thumbsup:

[bensmom]

It's basically about eliminating extra steps to keep things simple -- when you can get from here to there without going out of your way, it just makes sense.... The fewer the steps the better: the D ring's sole purpose it merely to be able to use the tether RF, it's just not intended for FF use & why would you want to do something more than necessary when the easy way works great? ;) Reference Ulrike's post when you call your dealership and/or vehicle manufacturer, it shouldn't really be a hassle to get the tether anchor :thumbsup:

I don't claim to understand all of the physics involved in crashes, but I think it's more than just keeping things simple. The tether anchor that you are using needs to be strong enough to withstand the crash forces involved in a forward facing crash. The carseat is going to continue moving forward when you crash, and it's going to pull on the tether anchor (at a force equal to the mass of the seat + kid times the acceleration, or something like that). When you use the D-ring, you aren't necessarily going to be able to wrap that strap around something that is strong enough to withstand these forces. That's also why in SUV's and similar vehicles, you need to make sure that you are actually using tether anchors and not just cargo tie downs.

Hopefully someone with a better engineering background can fill in more details.

[UlrikeDG]

I asked on the CPSP list, and Britax might have the part for you. You'll have to call them and ask (1-888-4-BRITAX).

If not, EZ-On has a kit you can buy that has the anchor bracket. You should still use the bolt and spacers from VW, as they're designed to fit your vehicle specifically. Here's the EZ-On info:Yes the tether anchor E-Z-ON sells is the same one we provide with the Kid Y and sell for less. $3.75 for the whole kit. Just email info@safetangel.com so we can send them out. We might add it to our website soon to buy separately if there is a demand.

The kit comes:
7/16 x 1 1/2 bolt
anchor bracket
2 3/8 safety washer
lock washer, nut

[Defrost]

I don't claim to understand all of the physics involved in crashes, but I think it's more than just keeping things simple. The tether anchor that you are using needs to be strong enough to withstand the crash forces involved in a forward facing crash.

I'm not 100% certain on this one, either, but I do agree - I don't think the D-rings are designed to support the forces of a FF-seat during a crash. I've had several D-rings, and the metal "D" is about the same weight and design as a simple locking clip - and locking clips are known to fail in crashes (I believe they're supposed to, actually).

[Defrost]

I asked on the CPSP list, and Britax might have the part for you. You'll have to call them and ask (1-888-4-BRITAX).

If not, EZ-On has a kit you can buy that has the anchor bracket. You should still use the bolt and spacers from VW, as they're designed to fit your vehicle specifically. Here's the EZ-On info:

I swear I remember my instruction manual specifically says you can't use their tether anchor with anything besides their products... of course, that info may have changed, and I'd assume the email you got from to be more accurate!

Hm... just re-checked and I can't find the reference. Apparently I'm nuts. ;)

[UlrikeDG]

Well, it was an EZ-On rep who sent me that info, so apparently, they don't mind too much.

I would, however, re-emphasize that whenever possible, you should use the parts provided by the vehicle manufacturer. Bolt sizes do vary from kit to kit, so you're likely to get the best protection from the kit that was tested with your vehicle. The anchor bracket itself really should be pretty universal, but it's still a PITB that VW doesn't have one they'll provide for retrofitting.

[UlrikeDG]

I got one more response:For the 1992 Cabriolet, please have her use part number 443 887 269 as the "universal bracket".

[netarc]

Thanks, folks - I found the VW Tech Bulletin here (http://www.idisagree.org/Passat/TSBs/SelfIdentified/69-01-01%20LATCH%20Child%20Seat%20Directions.pdf).

Ulrike, re: your comment...
For the 1992 Cabriolet, please have her use part number 443 887 269 as the "universal bracket".
...was this from VW, or from EZ-On (it seems to be a VW part #)

I'm a little confused between the "anchor bracket" (which the VW tech bulletin calls out and gives the parts list for on page 12, and your note that "VW recommends using a universal anchor provided by the seat manufacturer" ... what is this universal anchor, would not the VW parts be sufficient to create an anchor point to which the Britax's tether would attach?

[UlrikeDG]

That last post (443 887 269) was a VW part number. I'm pretty sure the person who sent it was a VW employee, but she didn't say so outright. The LATCH manual did not list a part number for the actual anchor bracket. Apparently, their original recommendation (which did make sense back in '92) was to use the bracket that comes with your seat. Because vehicles are now required to come with tether anchors, seat manufacturers no longer provide them with their seats, so it's not nearly as sensible now as it was 10+ years ago, and the most recent info I had didn't include the part number, so I had to do some digging to find out that it was even an option.

Anyway, it looks like you can get the entire kit from VW and have it installed, so you're good to go. Sorry it took half a dozen posts to get you there. ;)