So.. LATCH limits...

Baylor

New member

• Mar 23, 2012

• #1

Today as I was buckling my son in I was looking at my LATCH anchors, and thinking I wonder why its just 48lbs...

In my non CPST mind, They seem like the strongest way to anchor a carseat.

Have they ever failed that anyone knows of?

It just seems that they could take way more than 48 lbs...

All thoughts welcome.

More of a pondering post than a questioning post.

 

glockchick

New member

• Mar 23, 2012

• #2

Perhaps it's not the anchors, but the straps. LATCH straps are really thin compared to the seat belt that is rated to 350 lbs.

Or more likely it's that the anchors haven't been tested past 48 lbs if that's the vehicle's limit and not the csr limit.

 

cookie123

New member

• Mar 23, 2012

• #3

I wonder if the seat would hold up to the latch strap if the weight were more.

 

Baylor

New member

• Mar 23, 2012

• #4

glockchick said:

Perhaps it's not the anchors, but the straps. LATCH straps are really thin compared to the seat belt that is rated to 350 lbs.

Or more likely it's that the anchors haven't been tested past 48 lbs if that's the vehicle's limit and not the csr limit.

Click to expand...

Makes perfect sense. I just keep thinking if they are welded to the structure of car they have to be stronger than that.

 

jeminijad

New member

• Mar 23, 2012

• #5

Baylor, I think the same thing. How can a metal U welded directly onto the frame of the car be able to withstand less force than all of the pieces of a seatbelt assembly, which is in turn bolted onto the frame of the car?

Is this just an artefact of the 40lbs straight into booster mentality?

The idea that it is the LATCH straps, rather than the anchors themselves, makes sense. The Diono super LATCH was thicker.

 

Qarin

New member

• Mar 23, 2012

• #6

Why do you think they're welded? How is welding automatically so strong, where bolts are not? They're not, and it wouldn't be anyway.

Here is a picture of the driver-side latch bar from a 2005 Toyota sedan:

Seatbelts are designed and engineered to withstand adult weight crash forces- those little pieces of metal are, presumably, not.

 

Baylor

New member

• Mar 23, 2012

• #7

Qarin said:

Why do you think they're welded? How is welding automatically so strong, where bolts are not? They're not, and it wouldn't be anyway.

Here is a picture of the driver-side latch bar from a 2005 Toyota sedan:

Seatbelts are designed and engineered to withstand adult weight crash forces- those little pieces of metal are, presumably, not.

Click to expand...

Hmm I don't know why I just have assumed they were welded. Bolts are strong also.

This just sits in my brain and it makes sense to me that they would hold more than 48 lbs plus car seat.

auto correct hates me

 

morninglori

New member

• Mar 23, 2012

• #8

The latch bars are bolted to the vehicle- it's actually a FMVSS 225 requirement that that the anchorage bars are "Are part of the vehicle, such that they can only be removed by use of a tool, such as a screwdriver or wrench".

Bolted joints are more ductile, welded joints are more brittle. Ductile/bolted joints perform much better under the dynamic load of a vehicle crash. Welds are also more rigid, and are more affected by fatigue (all those bumps and bounces when driving) than a torqued bolt.

Where the bolts are attached to could be the difference. Perhaps the frame is less reinforced where the LATCH bar is bolted to than where the seatbelt anchor bolts are?

The weak part of the LATCH system on the carseat side might also be the LATCH connector rather than the webbing strap? When SK/Diono made the superlatch, they significantly changed the connector to get the extra lbs - can't tell how much they changed the strap, but if you look at the superlatch connector, you see 4 metal plates that attach over the LATCH bar, the regular LATCH connectors only have 1.

 

Spam

New member

• Mar 23, 2012

• #9

I wish they had a higher weight limit, it would make loading in gma's van a little easier if the captain chairs could flip forward with the seats on them but since my 3.5 yr old just passed the 50lb mark it's a no go. I also don't get the weight limit on top tethers on some seats.

 

luckyclov

New member

• Mar 23, 2012

• #10

Seatbelts are designed and engineered to withstand adult weight crash forces- those little pieces of metal are, presumably, not.

Click to expand...

Yeah, that.

I actually prefer to use the seatbelt, personally, as often as I can and frequently discontinue LA use far before whatever limit I'm supposed to comply with is maxed out. Between the difference in LATCH strap webbing/connectors and not really knowing a whole lot about LAs and applicable force/weight testing, it tends to ease my gut a bit.

 

Pixels

New member

• Mar 23, 2012

• #11

Yes, I have seen a failure of a lower anchor. It was definitely a misuse scenario, but it can happen. The anchor pulled out of the vehicle, releasing the lower anchor strap from the connector and the seat went flying.

The anchors in the vehicles are only required to hold so much force. It doesn't really matter if it's welded or bolted, if it's a little tiny connection it won't be as strong as, say, the connections in a bridge. Since they are only required to hold so much, that's all that can be guaranteed. Anything more than that is anybody's guess if it will hold or not.

 

S

Syllieann

New member

• Mar 23, 2012

• #12

Based on superlatch info, I'd bet (but not w/ my kids life) those hold at least 105# total (seat plus child) if the CR's latch system were made compatible. The avg parent can get a much tighter installation with latch than w/ SB. We all know that the tighter the child is coupled to the vehicle, the more of the force the vehicle can ride down for the child. Therefore, it would be beneficial to use latch when possible. I think it would be worth testing existing anchors to higher standards instead of setting artificially low limits that force parents to switch to sb earlier and in some cases, it makes the difference of where the seating location is and how closely parents can follow best practice-esp. utilizing center seating positions. In my van I can't take advantage of the center seating for the pass side capt chair if I want to install a hwh seat w/ SB and still use the 3rd row, so the low limits will force an outside installation instead of center.

 

Pixels

New member

• Mar 23, 2012

• #13

NHTSA is imposing an across-the-board 65 pound combined (child plus seat) limit, effective less than two years from now. All child restraints will be clearly labeled with a lower anchor limit child weight. That labeled weight, plus the weight of the seat, must not exceed 65 pounds.

 

glockchick

New member

• Mar 23, 2012

• #14

I was going to come back and say that correctly torqued bolts can be stronger than welds easily, but Qarin beat me to it. Plus, it is infinitely easier to ensure the uniformity of a bolt than a weld.